diff --git a/integration/side-effects/snapshots/common/esm2015.js b/integration/side-effects/snapshots/common/esm2015.js
index 05c0877c59..595d8ae0af 100644
--- a/integration/side-effects/snapshots/common/esm2015.js
+++ b/integration/side-effects/snapshots/common/esm2015.js
@@ -1,3 +1 @@
 import "@angular/core";
-
-import "rxjs";
diff --git a/integration/side-effects/snapshots/common/esm5.js b/integration/side-effects/snapshots/common/esm5.js
index e7e3a29ff8..05d504f1d4 100644
--- a/integration/side-effects/snapshots/common/esm5.js
+++ b/integration/side-effects/snapshots/common/esm5.js
@@ -1,5 +1,3 @@
 import "tslib";
 
 import "@angular/core";
-
-import "rxjs";
diff --git a/packages/common/src/pipes/async_pipe.ts b/packages/common/src/pipes/async_pipe.ts
index 45337cbc73..40d565d2f1 100644
--- a/packages/common/src/pipes/async_pipe.ts
+++ b/packages/common/src/pipes/async_pipe.ts
@@ -6,8 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {ChangeDetectorRef, EventEmitter, OnDestroy, Pipe, PipeTransform, WrappedValue, ɵisPromise, ɵlooseIdentical} from '@angular/core';
-import {Observable, SubscriptionLike, isObservable} from 'rxjs';
+import {ChangeDetectorRef, EventEmitter, OnDestroy, Pipe, PipeTransform, WrappedValue, ɵisObservable, ɵisPromise, ɵlooseIdentical} from '@angular/core';
+import {Observable, SubscriptionLike} from 'rxjs';
 import {invalidPipeArgumentError} from './invalid_pipe_argument_error';
 
 interface SubscriptionStrategy {
@@ -122,7 +122,7 @@ export class AsyncPipe implements OnDestroy, PipeTransform {
       return _promiseStrategy;
     }
 
-    if (isObservable(obj)) {
+    if (ɵisObservable(obj)) {
       return _observableStrategy;
     }
 
diff --git a/packages/core/src/core_private_export.ts b/packages/core/src/core_private_export.ts
index 99807e1a7c..fab88f1b34 100644
--- a/packages/core/src/core_private_export.ts
+++ b/packages/core/src/core_private_export.ts
@@ -30,7 +30,7 @@ export {global as ɵglobal} from './util/global';
 export {looseIdentical as ɵlooseIdentical,} from './util/comparison';
 export {stringify as ɵstringify} from './util/stringify';
 export {makeDecorator as ɵmakeDecorator} from './util/decorators';
-export {isPromise as ɵisPromise} from './util/lang';
+export {isObservable as ɵisObservable, isPromise as ɵisPromise} from './util/lang';
 export {clearOverrides as ɵclearOverrides, initServicesIfNeeded as ɵinitServicesIfNeeded, overrideComponentView as ɵoverrideComponentView, overrideProvider as ɵoverrideProvider} from './view/index';
 export {NOT_FOUND_CHECK_ONLY_ELEMENT_INJECTOR as ɵNOT_FOUND_CHECK_ONLY_ELEMENT_INJECTOR} from './view/provider';
 export {LocaleDataIndex as ɵLocaleDataIndex, CurrencyIndex as ɵCurrencyIndex, ExtraLocaleDataIndex as ɵExtraLocaleDataIndex, getLocalePluralCase as ɵgetLocalePluralCase, findLocaleData as ɵfindLocaleData, registerLocaleData as ɵregisterLocaleData, unregisterAllLocaleData as ɵunregisterLocaleData} from './i18n/locale_data_api';
diff --git a/packages/core/src/render3/instructions/listener.ts b/packages/core/src/render3/instructions/listener.ts
index 0c8d871647..37bc71bd8d 100644
--- a/packages/core/src/render3/instructions/listener.ts
+++ b/packages/core/src/render3/instructions/listener.ts
@@ -6,8 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {isObservable} from 'rxjs';
+
 import {assertDataInRange} from '../../util/assert';
+import {isObservable} from '../../util/lang';
 import {EMPTY_OBJ} from '../empty';
 import {PropertyAliasValue, TNode, TNodeFlags, TNodeType} from '../interfaces/node';
 import {GlobalTargetResolver, RElement, Renderer3, isProceduralRenderer} from '../interfaces/renderer';
diff --git a/packages/core/src/util/BUILD.bazel b/packages/core/src/util/BUILD.bazel
index 0862fc5a20..3ea2b343c1 100644
--- a/packages/core/src/util/BUILD.bazel
+++ b/packages/core/src/util/BUILD.bazel
@@ -15,5 +15,6 @@ ts_library(
     deps = [
         "//packages:types",
         "//packages/core/src/interface",
+        "@npm//rxjs",
     ],
 )
diff --git a/packages/core/src/util/lang.ts b/packages/core/src/util/lang.ts
index 6cf4316a83..b6631e84d0 100644
--- a/packages/core/src/util/lang.ts
+++ b/packages/core/src/util/lang.ts
@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {Observable} from 'rxjs';
+
 /**
  * Determine if the argument is shaped like a Promise
  */
@@ -14,3 +16,12 @@ export function isPromise(obj: any): obj is Promise<any> {
   // It's up to the caller to ensure that obj.then conforms to the spec
   return !!obj && typeof obj.then === 'function';
 }
+
+/**
+ * Determine if the argument is an Observable
+ */
+export function isObservable(obj: any | Observable<any>): obj is Observable<any> {
+  // TODO: use isObservable once we update pass rxjs 6.1
+  // https://github.com/ReactiveX/rxjs/blob/master/CHANGELOG.md#610-2018-05-03
+  return !!obj && typeof obj.subscribe === 'function';
+}
diff --git a/packages/core/src/view/provider.ts b/packages/core/src/view/provider.ts
index 2c10555612..f8421a03bc 100644
--- a/packages/core/src/view/provider.ts
+++ b/packages/core/src/view/provider.ts
@@ -6,13 +6,13 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {isObservable} from 'rxjs';
 import {ChangeDetectorRef, SimpleChange, SimpleChanges, WrappedValue} from '../change_detection/change_detection';
 import {INJECTOR, Injector, resolveForwardRef} from '../di';
 import {ElementRef} from '../linker/element_ref';
 import {TemplateRef} from '../linker/template_ref';
 import {ViewContainerRef} from '../linker/view_container_ref';
 import {Renderer2} from '../render/api';
+import {isObservable} from '../util/lang';
 import {stringify} from '../util/stringify';
 
 import {createChangeDetectorRef, createInjector} from './refs';
diff --git a/packages/core/test/util/lang_spec.ts b/packages/core/test/util/lang_spec.ts
index 19aade5c38..73086b09cf 100644
--- a/packages/core/test/util/lang_spec.ts
+++ b/packages/core/test/util/lang_spec.ts
@@ -5,7 +5,8 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {isPromise} from '@angular/core/src/util/lang';
+import {isObservable, isPromise} from '@angular/core/src/util/lang';
+import {of } from 'rxjs';
 
 {
   describe('isPromise', () => {
@@ -25,4 +26,22 @@ import {isPromise} from '@angular/core/src/util/lang';
       expect(isPromise(null)).toEqual(false);
     });
   });
+
+  describe('isObservable', () => {
+    it('should be true for an Observable', () => expect(isObservable(of (true))).toEqual(true));
+
+    it('should be true if the argument is the object with subscribe function',
+       () => expect(isObservable({subscribe: () => {}})).toEqual(true));
+
+    it('should be false if the argument is undefined',
+       () => expect(isObservable(undefined)).toEqual(false));
+
+    it('should be false if the argument is null', () => expect(isObservable(null)).toEqual(false));
+
+    it('should be false if the argument is an object',
+       () => expect(isObservable({})).toEqual(false));
+
+    it('should be false if the argument is a function',
+       () => expect(isObservable(() => {})).toEqual(false));
+  });
 }
diff --git a/packages/core/test/view/BUILD.bazel b/packages/core/test/view/BUILD.bazel
index ca16bb9be6..481f1bcdf1 100644
--- a/packages/core/test/view/BUILD.bazel
+++ b/packages/core/test/view/BUILD.bazel
@@ -17,7 +17,6 @@ ts_library(
         "//packages/core/testing",
         "//packages/platform-browser",
         "//packages/private/testing",
-        "@npm//rxjs",
     ],
 )
 
diff --git a/packages/core/test/view/provider_spec.ts b/packages/core/test/view/provider_spec.ts
index 9a61e4051e..cab5b26bc8 100644
--- a/packages/core/test/view/provider_spec.ts
+++ b/packages/core/test/view/provider_spec.ts
@@ -6,7 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Observable} from 'rxjs';
 import {AfterContentChecked, AfterContentInit, AfterViewChecked, AfterViewInit, ChangeDetectorRef, DoCheck, ElementRef, ErrorHandler, EventEmitter, Injector, OnChanges, OnDestroy, OnInit, Renderer2, SimpleChange, TemplateRef, ViewContainerRef,} from '@angular/core';
 import {getDebugContext} from '@angular/core/src/errors';
 import {ArgumentType, DepFlags, NodeFlags, Services, anchorDef, asElementData, directiveDef, elementDef, providerDef, textDef} from '@angular/core/src/view/index';
@@ -342,11 +341,13 @@ import {ARG_TYPE_VALUES, checkNodeInlineOrDynamic, createRootView, createAndGetR
         let unsubscribeSpy: any;
 
         class SomeService {
-          emitter = new Observable((callback: any) => {
-            const subscription = emitter.subscribe(callback);
-            unsubscribeSpy = spyOn(subscription, 'unsubscribe').and.callThrough();
-            return subscription;
-          });
+          emitter = {
+            subscribe: (callback: any) => {
+              const subscription = emitter.subscribe(callback);
+              unsubscribeSpy = spyOn(subscription, 'unsubscribe').and.callThrough();
+              return subscription;
+            }
+          };
         }
 
         const handleEvent = jasmine.createSpy('handleEvent');
diff --git a/packages/forms/src/validators.ts b/packages/forms/src/validators.ts
index 0806954b61..116d306e86 100644
--- a/packages/forms/src/validators.ts
+++ b/packages/forms/src/validators.ts
@@ -6,8 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {InjectionToken, ɵisPromise as isPromise} from '@angular/core';
-import {Observable, forkJoin, from, isObservable} from 'rxjs';
+import {InjectionToken, ɵisObservable as isObservable, ɵisPromise as isPromise} from '@angular/core';
+import {Observable, forkJoin, from} from 'rxjs';
 import {map} from 'rxjs/operators';
 import {AsyncValidatorFn, ValidationErrors, Validator, ValidatorFn} from './directives/validators';
 import {AbstractControl, FormControl} from './model';
diff --git a/packages/router/src/utils/collection.ts b/packages/router/src/utils/collection.ts
index 95af5c1390..74fbc81420 100644
--- a/packages/router/src/utils/collection.ts
+++ b/packages/router/src/utils/collection.ts
@@ -6,8 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {NgModuleFactory, ɵisPromise as isPromise} from '@angular/core';
-import {Observable, from, isObservable, of } from 'rxjs';
+import {NgModuleFactory, ɵisObservable as isObservable, ɵisPromise as isPromise} from '@angular/core';
+import {Observable, from, of } from 'rxjs';
 import {concatAll, last as lastValue, map} from 'rxjs/operators';
 
 import {PRIMARY_OUTLET, Params} from '../shared';