diff --git a/projects/ngqp-demo/src/app/docs-items/configuration/query-param/query-param-configuration-docs.component.html b/projects/ngqp-demo/src/app/docs-items/configuration/query-param/query-param-configuration-docs.component.html
index 84aca32..53dd155 100644
--- a/projects/ngqp-demo/src/app/docs-items/configuration/query-param/query-param-configuration-docs.component.html
+++ b/projects/ngqp-demo/src/app/docs-items/configuration/query-param/query-param-configuration-docs.component.html
@@ -20,6 +20,18 @@ <h2>Serializing and deserializing</h2>
         provide your own (de-)serializers, you can pass them to <span apiDocsLink>QueryParamBuilder#param</span>.
     </p>
     <demo-serializer-example></demo-serializer-example>
+    <div class="alert alert-info">
+        <p>
+            Deserializers can also be asynchronous by returning an Observable instead. This can be useful, e.g., if you
+            have a user's name in the URL and need to deserialize it into a user object, but fetching the list of users
+            is an asynchronous operation.
+        </p>
+        <p>
+            Note that for asynchronous deserializers, ngqp will use the <em>first</em> emitted value rather than the
+            last one. Furthermore, the <code>valueChanges</code> observables will only emit after the deserializer has
+            emitted.
+        </p>
+    </div>
 
     <docs-fragment fragment="multi">
         <h2>Components with multiple values</h2>
diff --git a/projects/ngqp-demo/src/app/home/home.component.ts b/projects/ngqp-demo/src/app/home/home.component.ts
index 43aed8e..82ccef9 100644
--- a/projects/ngqp-demo/src/app/home/home.component.ts
+++ b/projects/ngqp-demo/src/app/home/home.component.ts
@@ -1,5 +1,5 @@
 import { Component } from '@angular/core';
-import { createStringDeserializer, QueryParamBuilder, QueryParamGroup } from '@ngqp/core';
+import { QueryParamBuilder, QueryParamGroup } from '@ngqp/core';
 import { faAlignLeft, faCogs, faGlassCheers, faHeart, IconDefinition } from '@fortawesome/free-solid-svg-icons';
 import { faGithub } from '@fortawesome/free-brands-svg-icons';
 
diff --git a/projects/ngqp/core/src/lib/directives/query-param-group.service.ts b/projects/ngqp/core/src/lib/directives/query-param-group.service.ts
index c512343..4ff692f 100644
--- a/projects/ngqp/core/src/lib/directives/query-param-group.service.ts
+++ b/projects/ngqp/core/src/lib/directives/query-param-group.service.ts
@@ -1,6 +1,6 @@
 import { Inject, Injectable, isDevMode, OnDestroy, Optional } from '@angular/core';
 import { Params } from '@angular/router';
-import { EMPTY, from, Observable, Subject, zip } from 'rxjs';
+import { EMPTY, forkJoin, from, Observable, Subject, zip } from 'rxjs';
 import {
     catchError,
     concatMap,
@@ -15,7 +15,7 @@ import {
 } from 'rxjs/operators';
 import { compareParamMaps, filterParamMap, isMissing, isPresent, NOP } from '../util';
 import { QueryParamGroup } from '../model/query-param-group';
-import { MultiQueryParam, QueryParam, PartitionedQueryParam } from '../model/query-param';
+import { MultiQueryParam, PartitionedQueryParam, QueryParam } from '../model/query-param';
 import { NGQP_ROUTER_ADAPTER, NGQP_ROUTER_OPTIONS, RouterAdapter, RouterOptions } from '../router-adapter/router-adapter.interface';
 import { QueryParamAccessor } from './query-param-accessor.interface';
 
@@ -226,32 +226,49 @@ export class QueryParamGroupService implements OnDestroy {
                     return compareParamMaps(filterParamMap(previousMap, keys), filterParamMap(currentMap, keys));
                 }),
             )),
-            takeUntil(this.destroy$),
-        ).subscribe(queryParamMap => {
-            const synthetic = this.isSyntheticNavigation();
-            const groupValue: Record<string, unknown> = {};
-
-            Object.keys(this.getQueryParamGroup().queryParams).forEach(queryParamName => {
-                const partitionedQueryParam = this.getQueryParamAsPartition(queryParamName);
-                const newValues = partitionedQueryParam.queryParams.map(queryParam => isMultiQueryParam<unknown>(queryParam)
-                    ? queryParam.deserializeValue(queryParamMap.getAll(queryParam.urlParam))
-                    : queryParam.deserializeValue(queryParamMap.get(queryParam.urlParam))
+            switchMap(queryParamMap => {
+                // We need to capture this right here since this is only set during the on-going navigation.
+                const synthetic = this.isSyntheticNavigation();
+                const queryParamNames = Object.keys(this.getQueryParamGroup().queryParams);
+
+                return forkJoin<Record<string, unknown>>(...queryParamNames
+                    .map(queryParamName => {
+                        const partitionedQueryParam = this.getQueryParamAsPartition(queryParamName);
+
+                        return forkJoin<unknown>(...partitionedQueryParam.queryParams
+                            .map(queryParam => isMultiQueryParam<unknown>(queryParam)
+                                ? queryParam.deserializeValue(queryParamMap.getAll(queryParam.urlParam))
+                                : queryParam.deserializeValue(queryParamMap.get(queryParam.urlParam))
+                            )
+                        ).pipe(
+                            map(newValues => partitionedQueryParam.reduce(newValues)),
+                            tap(newValue => {
+                                const directives = this.directives.get(queryParamName);
+                                if (directives) {
+                                    directives.forEach(directive => directive.valueAccessor.writeValue(newValue));
+                                }
+                            }),
+                            map(newValue => {
+                                return { [ queryParamName ]: newValue };
+                            }),
+                            takeUntil(this.destroy$),
+                        );
+                    })
+                ).pipe(
+                    map((values: Record<string, unknown>[]) => values.reduce((groupValue, value) => {
+                        return {
+                            ...groupValue,
+                            ...value,
+                        };
+                    }, {})),
+                    tap(groupValue => this.getQueryParamGroup().setValue(groupValue, {
+                        emitEvent: !synthetic,
+                        emitModelToViewChange: false,
+                    })),
                 );
-                const newValue = partitionedQueryParam.reduce(newValues);
-
-                const directives = this.directives.get(queryParamName);
-                if (directives) {
-                    directives.forEach(directive => directive.valueAccessor.writeValue(newValue));
-                }
-
-                groupValue[ queryParamName ] = newValue;
-            });
-
-            this.getQueryParamGroup().setValue(groupValue, {
-                emitEvent: !synthetic,
-                emitModelToViewChange: false,
-            });
-        });
+            }),
+            takeUntil(this.destroy$),
+        ).subscribe();
     }
 
     /** Listens for newly added parameters and starts synchronization for them. */
@@ -350,7 +367,7 @@ export class QueryParamGroupService implements OnDestroy {
 
         return {
             ...(this.globalRouterOptions || {}),
-            ...groupOptions,
+            ...(groupOptions || {}),
         };
     }
 
diff --git a/projects/ngqp/core/src/lib/model/query-param.ts b/projects/ngqp/core/src/lib/model/query-param.ts
index 37b33b7..2d74214 100644
--- a/projects/ngqp/core/src/lib/model/query-param.ts
+++ b/projects/ngqp/core/src/lib/model/query-param.ts
@@ -1,5 +1,6 @@
-import { Observable, Subject } from 'rxjs';
-import { areEqualUsing, isFunction, isMissing, isPresent, undefinedToNull, wrapTryCatch } from '../util';
+import { forkJoin, isObservable, Observable, of, Subject } from 'rxjs';
+import { first } from 'rxjs/operators';
+import { areEqualUsing, isFunction, isMissing, isPresent, undefinedToNull, wrapIntoObservable, wrapTryCatch } from '../util';
 import { Comparator, OnChangeFunction, ParamCombinator, ParamDeserializer, ParamSerializer, Partitioner, Reducer } from '../types';
 import { QueryParamGroup } from './query-param-group';
 import { MultiQueryParamOpts, PartitionedQueryParamOpts, QueryParamOpts, QueryParamOptsBase } from './query-param-opts';
@@ -117,12 +118,6 @@ export abstract class AbstractQueryParam<U, T> extends AbstractQueryParamBase<T>
         this.combineWith = combineWith;
     }
 
-    /** @internal */
-    public abstract serializeValue(value: T | null): (string | null) | (string | null)[];
-
-    /** @internal */
-    public abstract deserializeValue(value: (string | null) | (string | null)[]): T | null;
-
     /**
      * Updates the value of this parameter.
      *
@@ -180,12 +175,12 @@ export class QueryParam<T> extends AbstractQueryParam<T | null, T | null> implem
     }
 
     /** @internal */
-    public deserializeValue(value: string | null): T | null {
+    public deserializeValue(value: string | null): Observable<T | null> {
         if (this.emptyOn !== undefined && value === null) {
-            return this.emptyOn;
+            return of(this.emptyOn);
         }
 
-        return this.deserialize(value);
+        return wrapIntoObservable(this.deserialize(value)).pipe(first());
     }
 
 }
@@ -212,12 +207,14 @@ export class MultiQueryParam<T> extends AbstractQueryParam<T | null, (T | null)[
     }
 
     /** @internal */
-    public deserializeValue(value: (string | null)[] | null): (T | null)[] | null {
-        if (this.emptyOn !== undefined && (value || []).length === 0) {
-            return this.emptyOn;
+    public deserializeValue(values: (string | null)[] | null): Observable<(T | null)[] | null> {
+        if (this.emptyOn !== undefined && (values || []).length === 0) {
+            return of(this.emptyOn);
         }
 
-        return (value || []).map(this.deserialize.bind(this));
+        return forkJoin<T | null>(...(values || [])
+            .map(value => wrapIntoObservable(this.deserialize(value)).pipe(first()))
+        );
     }
 
 }
diff --git a/projects/ngqp/core/src/lib/types.ts b/projects/ngqp/core/src/lib/types.ts
index 1a168b9..1404782 100644
--- a/projects/ngqp/core/src/lib/types.ts
+++ b/projects/ngqp/core/src/lib/types.ts
@@ -1,4 +1,5 @@
 import { Params } from '@angular/router';
+import { Observable } from 'rxjs';
 
 /**
  * A serializer defines how the represented form control's
@@ -10,7 +11,7 @@ export type ParamSerializer<T> = (model: T | null) => string | null;
  * A deserializer defines how a URL parameter is converted
  * into the represented form control's value.
  */
-export type ParamDeserializer<T> = (value: string | null) => T | null;
+export type ParamDeserializer<T> = (value: string | null) => (T | null) | Observable<T | null>;
 
 /**
  * A partitioner can split a value into an array of parts.
diff --git a/projects/ngqp/core/src/lib/util.spec.ts b/projects/ngqp/core/src/lib/util.spec.ts
index 7a600b3..bb2899f 100644
--- a/projects/ngqp/core/src/lib/util.spec.ts
+++ b/projects/ngqp/core/src/lib/util.spec.ts
@@ -1,4 +1,5 @@
 import { convertToParamMap, Params } from '@angular/router';
+import { of } from 'rxjs';
 import {
     areEqualUsing,
     compareParamMaps,
@@ -9,6 +10,7 @@ import {
     isPresent,
     LOOSE_IDENTITY_COMPARATOR,
     undefinedToNull,
+    wrapIntoObservable,
     wrapTryCatch
 } from './util';
 import { Comparator } from './types';
@@ -266,4 +268,27 @@ describe(compareParamMaps.name, () => {
             { a: [ 'a2', 'a1' ] },
         )).toBe(true);
     });
+});
+
+describe(wrapIntoObservable.name, async () => {
+    it('wraps null', async () => {
+        const obs$ = wrapIntoObservable(null);
+        expect(obs$).toBeDefined();
+
+        obs$.subscribe(v => expect(v).toBe(null));
+    });
+
+    it('wraps a primitive value', async () => {
+        const obs$ = wrapIntoObservable(42);
+        expect(obs$).toBeDefined();
+
+        obs$.subscribe(v => expect(v).toBe(42));
+    });
+
+    it('does not wrap an observable', async () => {
+        const obs$ = wrapIntoObservable(of(42));
+        expect(obs$).toBeDefined();
+
+        obs$.subscribe(v => expect(v).toBe(42));
+    });
 });
\ No newline at end of file
diff --git a/projects/ngqp/core/src/lib/util.ts b/projects/ngqp/core/src/lib/util.ts
index 2509765..81de7cd 100644
--- a/projects/ngqp/core/src/lib/util.ts
+++ b/projects/ngqp/core/src/lib/util.ts
@@ -1,4 +1,5 @@
 import { convertToParamMap, ParamMap, Params } from '@angular/router';
+import { isObservable, Observable, of } from 'rxjs';
 import { Comparator } from './types';
 
 /** @internal */
@@ -96,4 +97,13 @@ export function compareStringArraysUnordered(first: string[], second: string[]):
     const sortedFirst = first.sort();
     const sortedSecond = second.sort();
     return sortedFirst.every((firstKey, index) => firstKey === sortedSecond[index]);
+}
+
+/** @internal */
+export function wrapIntoObservable<T>(input: T | Observable<T>): Observable<T> {
+    if (isObservable(input)) {
+        return input;
+    }
+
+    return of(input);
 }
\ No newline at end of file
diff --git a/projects/ngqp/core/src/test/serialize-deserialize.spec.ts b/projects/ngqp/core/src/test/serialize-deserialize.spec.ts
index dd3de97..eb62535 100644
--- a/projects/ngqp/core/src/test/serialize-deserialize.spec.ts
+++ b/projects/ngqp/core/src/test/serialize-deserialize.spec.ts
@@ -2,6 +2,8 @@ import { Component } from '@angular/core';
 import { Router } from '@angular/router';
 import { async, ComponentFixture, fakeAsync, TestBed, tick } from '@angular/core/testing';
 import { RouterTestingModule } from '@angular/router/testing';
+import { of } from 'rxjs';
+import { delay } from 'rxjs/operators';
 import { QueryParamBuilder, QueryParamGroup, QueryParamModule } from '../public_api';
 import { setupNavigationWarnStub } from './util';
 
@@ -27,6 +29,28 @@ class BasicTestComponent {
 
 }
 
+@Component({
+    template: `
+        <div [queryParamGroup]="paramGroup">
+            <input type="text" queryParamName="param" />
+        </div>
+    `,
+})
+class AsyncTestComponent {
+
+    public paramGroup: QueryParamGroup;
+
+    constructor(private qpb: QueryParamBuilder) {
+        this.paramGroup = qpb.group({
+            param: qpb.stringParam('q', {
+                serialize: value => value ? value.toUpperCase() : null,
+                deserialize: value => of(value ? value.toLowerCase() : null).pipe(delay(500)),
+            }),
+        });
+    }
+
+}
+
 describe('(de-)serialize', () => {
     let fixture: ComponentFixture<BasicTestComponent>;
     let component: BasicTestComponent;
@@ -72,6 +96,50 @@ describe('(de-)serialize', () => {
         router.navigateByUrl('/?q=TEST');
         tick();
 
+        expect(input.value).toBe('test');
+    }));
+});
+
+describe('asynchronous (de-)serialize', () => {
+    let fixture: ComponentFixture<AsyncTestComponent>;
+    let component: AsyncTestComponent;
+    let input: HTMLInputElement;
+    let router: Router;
+
+    beforeEach(() => setupNavigationWarnStub());
+
+    beforeEach(async(() => {
+        TestBed.configureTestingModule({
+            imports: [
+                RouterTestingModule.withRoutes([]),
+                QueryParamModule,
+            ],
+            declarations: [
+                AsyncTestComponent,
+            ],
+        });
+
+        router = TestBed.get(Router);
+        TestBed.compileComponents();
+        router.initialNavigation();
+    }));
+
+    beforeEach(() => {
+        fixture = TestBed.createComponent(AsyncTestComponent);
+        component = fixture.componentInstance;
+        fixture.detectChanges();
+
+        input = (fixture.nativeElement as HTMLElement).querySelector('input') as HTMLInputElement;
+        fixture.detectChanges();
+    });
+
+    it('applies the async deserializer when the URL changes', fakeAsync(() => {
+        router.navigateByUrl('/?q=TEST');
+
+        tick();
+        expect(input.value).toBe('');
+
+        tick(500);
         expect(input.value).toBe('test');
     }));
 });
\ No newline at end of file