diff --git a/packages/compiler-cli/src/ngtsc/annotations/src/component.ts b/packages/compiler-cli/src/ngtsc/annotations/src/component.ts
index ffa0da9954..8631e89645 100644
--- a/packages/compiler-cli/src/ngtsc/annotations/src/component.ts
+++ b/packages/compiler-cli/src/ngtsc/annotations/src/component.ts
@@ -266,8 +266,9 @@ export class ComponentDecoratorHandler implements
     const scope = this.scopeRegistry.lookupCompilationScopeAsRefs(node);
     const matcher = new SelectorMatcher<ScopeDirective<any>>();
     if (scope !== null) {
-      scope.directives.forEach(
-          ({selector, meta}) => { matcher.addSelectables(CssSelector.parse(selector), meta); });
+      for (const meta of scope.directives) {
+        matcher.addSelectables(CssSelector.parse(meta.selector), meta);
+      }
       ctx.addTemplate(node as ts.ClassDeclaration, meta.parsedTemplate, matcher);
     }
   }
@@ -284,8 +285,10 @@ export class ComponentDecoratorHandler implements
       // fully analyzed.
       const {pipes, containsForwardDecls} = scope;
       const directives: {selector: string, expression: Expression}[] = [];
-      scope.directives.forEach(
-          ({selector, meta}) => directives.push({selector, expression: meta.directive}));
+
+      for (const meta of scope.directives) {
+        directives.push({selector: meta.selector, expression: meta.directive});
+      }
       const wrapDirectivesAndPipesInClosure: boolean = !!containsForwardDecls;
       metadata = {...metadata, directives, pipes, wrapDirectivesAndPipesInClosure};
     }
diff --git a/packages/compiler-cli/src/ngtsc/annotations/src/selector_scope.ts b/packages/compiler-cli/src/ngtsc/annotations/src/selector_scope.ts
index 834635b021..2688d1a82a 100644
--- a/packages/compiler-cli/src/ngtsc/annotations/src/selector_scope.ts
+++ b/packages/compiler-cli/src/ngtsc/annotations/src/selector_scope.ts
@@ -31,7 +31,7 @@ export interface ModuleData {
  * context of some module.
  */
 export interface CompilationScope<T> {
-  directives: {selector: string, meta: ScopeDirective<T>}[];
+  directives: ScopeDirective<T>[];
   pipes: Map<string, T>;
   containsForwardDecls?: boolean;
 }
@@ -153,28 +153,38 @@ export class SelectorScopeRegistry {
     }
 
     // This is the first time the scope for this module is being computed.
-    const directives: {selector: string, meta: ScopeDirective<Reference<ts.Declaration>>}[] = [];
-    const pipes = new Map<string, Reference>();
+    const directives: ScopeDirective<Reference<ts.Declaration>>[] = [];
+    const pipes = new Map<string, Reference<ts.Declaration>>();
+
+    // Tracks which declarations already appear in the `CompilationScope`.
+    const seenSet = new Set<ts.Declaration>();
 
     // Process the declaration scope of the module, and lookup the selector of every declared type.
     // The initial value of ngModuleImportedFrom is 'null' which signifies that the NgModule
     // was not imported from a .d.ts source.
-    this.lookupScopesOrDie(module !, /* ngModuleImportedFrom */ null).compilation.forEach(ref => {
+    for (const ref of this.lookupScopesOrDie(module !, /* ngModuleImportedFrom */ null)
+             .compilation) {
       const node = ts.getOriginalNode(ref.node) as ts.Declaration;
 
+      // Track whether this `ts.Declaration` has been seen before.
+      if (seenSet.has(node)) {
+        continue;
+      } else {
+        seenSet.add(node);
+      }
+
       // Either the node represents a directive or a pipe. Look for both.
       const metadata = this.lookupDirectiveMetadata(ref);
       // Only directives/components with selectors get added to the scope.
-      if (metadata != null) {
-        directives.push({selector: metadata.selector, meta: {...metadata, directive: ref}});
-        return;
+      if (metadata !== null) {
+        directives.push({...metadata, directive: ref});
+      } else {
+        const name = this.lookupPipeName(node);
+        if (name !== null) {
+          pipes.set(name, ref);
+        }
       }
-
-      const name = this.lookupPipeName(node);
-      if (name != null) {
-        pipes.set(name, ref);
-      }
-    });
+    }
 
     const scope: CompilationScope<Reference> = {directives, pipes};
 
@@ -419,14 +429,13 @@ function absoluteModuleName(ref: Reference): string|null {
 }
 
 function convertDirectiveReferenceList(
-    input: {selector: string, meta: ScopeDirective<Reference>}[],
-    context: ts.SourceFile): {selector: string, meta: ScopeDirective<Expression>}[] {
-  return input.map(({selector, meta}) => {
+    input: ScopeDirective<Reference>[], context: ts.SourceFile): ScopeDirective<Expression>[] {
+  return input.map(meta => {
     const directive = meta.directive.toExpression(context);
     if (directive === null) {
       throw new Error(`Could not write expression to reference ${meta.directive.node}`);
     }
-    return {selector, meta: {...meta, directive}};
+    return {...meta, directive};
   });
 }
 
@@ -450,7 +459,7 @@ function convertScopeToExpressions(
   const pipes = convertPipeReferenceMap(scope.pipes, sourceContext);
   const declPointer = maybeUnwrapNameOfDeclaration(context);
   let containsForwardDecls = false;
-  directives.forEach(({selector, meta}) => {
+  directives.forEach(meta => {
     containsForwardDecls = containsForwardDecls ||
         isExpressionForwardReference(meta.directive, declPointer, sourceContext);
   });
diff --git a/packages/compiler-cli/test/ngtsc/fake_core/index.ts b/packages/compiler-cli/test/ngtsc/fake_core/index.ts
index ea784dec32..831831738d 100644
--- a/packages/compiler-cli/test/ngtsc/fake_core/index.ts
+++ b/packages/compiler-cli/test/ngtsc/fake_core/index.ts
@@ -60,4 +60,7 @@ export function forwardRef<T>(fn: () => T): T {
   return fn();
 }
 
-export interface SimpleChanges { [propName: string]: any; }
\ No newline at end of file
+export interface SimpleChanges { [propName: string]: any; }
+
+export type ɵNgModuleDefWithMeta<ModuleT, DeclarationsT, ImportsT, ExportsT> = any;
+export type ɵDirectiveDefWithMeta<DirT, SelectorT, ExportAsT, InputsT, OutputsT, QueriesT> = any;
diff --git a/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts b/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
index 79192f1d01..c3d79bb7fc 100644
--- a/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
+++ b/packages/compiler-cli/test/ngtsc/ngtsc_spec.ts
@@ -1078,4 +1078,40 @@ describe('ngtsc behavioral tests', () => {
 
     // Success is enough to indicate that this passes.
   });
+
+  it('should not emit multiple references to the same directive', () => {
+    env.tsconfig();
+    env.write('node_modules/external/index.d.ts', `
+      import {ɵDirectiveDefWithMeta, ɵNgModuleDefWithMeta} from '@angular/core';
+
+      export declare class ExternalDir {
+        static ngDirectiveDef: ɵDirectiveDefWithMeta<ExternalDir, '[test]', never, never, never, never>;
+      }
+
+      export declare class ExternalModule {
+        static ngModuleDef: ɵNgModuleDefWithMeta<ExternalModule, [typeof ExternalDir], never, [typeof ExternalDir]>;
+      }
+    `);
+    env.write('test.ts', `
+      import {Component, Directive, NgModule} from '@angular/core';
+      import {ExternalModule} from 'external';
+
+      @Component({
+        template: '<div test></div>',
+      })
+      class Cmp {}
+
+      @NgModule({
+        declarations: [Cmp],
+        // Multiple imports of the same module used to result in duplicate directive references
+        // in the output.
+        imports: [ExternalModule, ExternalModule],
+      })
+      class Module {}
+    `);
+
+    env.driveMain();
+    const jsContents = env.getContents('test.js');
+    expect(jsContents).toMatch(/directives: \[i1\.ExternalDir\]/);
+  });
 });