diff --git a/src/lib/dialog/dialog-content-directives.ts b/src/lib/dialog/dialog-content-directives.ts
index edca30a06c2b..5dec4d9dca9c 100644
--- a/src/lib/dialog/dialog-content-directives.ts
+++ b/src/lib/dialog/dialog-content-directives.ts
@@ -29,25 +29,19 @@ let dialogElementUid = 0;
   exportAs: 'matDialogClose',
   host: {
     '(click)': 'dialogRef.close(dialogResult)',
-    '[attr.aria-label]': '_hasAriaLabel ? ariaLabel : null',
+    '[attr.aria-label]': 'ariaLabel || null',
     'type': 'button', // Prevents accidental form submits.
   }
 })
 export class MatDialogClose implements OnInit, OnChanges {
   /** Screenreader label for the button. */
-  @Input('aria-label') ariaLabel: string = 'Close dialog';
+  @Input('aria-label') ariaLabel: string;
 
   /** Dialog close input. */
   @Input('mat-dialog-close') dialogResult: any;
 
   @Input('matDialogClose') _matDialogClose: any;
 
-  /**
-   * Whether the button should have an `aria-label`. Used for clearing the
-   * attribute to prevent it from being read instead of the button's text.
-   */
-  _hasAriaLabel?: boolean;
-
   constructor(
     @Optional() public dialogRef: MatDialogRef<any>,
     private _elementRef: ElementRef<HTMLElement>,
@@ -62,30 +56,14 @@ export class MatDialogClose implements OnInit, OnChanges {
       // be resolved at constructor time.
       this.dialogRef = getClosestDialog(this._elementRef, this._dialog.openDialogs)!;
     }
-
-    if (typeof this._hasAriaLabel === 'undefined') {
-      const element = this._elementRef.nativeElement;
-
-      if (element.hasAttribute('mat-icon-button')) {
-        this._hasAriaLabel = true;
-      } else {
-        const buttonTextContent = element.textContent;
-        this._hasAriaLabel = !buttonTextContent || buttonTextContent.trim().length === 0;
-      }
-    }
   }
 
   ngOnChanges(changes: SimpleChanges) {
-    const proxiedChange =
-        changes['_matDialogClose'] || changes['_matDialogCloseResult'];
+    const proxiedChange = changes['_matDialogClose'] || changes['_matDialogCloseResult'];
 
     if (proxiedChange) {
       this.dialogResult = proxiedChange.currentValue;
     }
-
-    if (changes['ariaLabel']) {
-      this._hasAriaLabel = !!changes['ariaLabel'].currentValue;
-    }
   }
 }
 
diff --git a/src/lib/dialog/dialog.md b/src/lib/dialog/dialog.md
index de198325bad3..9984e42e0145 100644
--- a/src/lib/dialog/dialog.md
+++ b/src/lib/dialog/dialog.md
@@ -154,6 +154,10 @@ a [focus trap](https://material.angular.io/cdk/a11y/overview#focustrap) to conta
 within itself. Once a dialog is closed, it will return focus to the element that was focused
 before the dialog was opened.
 
+If you're adding a close button that doesn't have text (e.g. a purely icon-based button), make sure
+that it has a meaningful `aria-label` so that users with assistive technology know what it is used
+for.
+
 #### Focus management
 By default, the first tabbable element within the dialog will receive focus upon open. This can
 be configured by setting the `cdkFocusInitial` attribute on another focusable element.
diff --git a/src/lib/dialog/dialog.spec.ts b/src/lib/dialog/dialog.spec.ts
index 246a1863ba0f..c6159bf2e844 100644
--- a/src/lib/dialog/dialog.spec.ts
+++ b/src/lib/dialog/dialog.spec.ts
@@ -1143,26 +1143,11 @@ describe('MatDialog', () => {
         expect(overlayContainerElement.querySelectorAll('.mat-dialog-container').length).toBe(1);
       });
 
-      it('should set an aria-label on a button without text', fakeAsync(() => {
-        let button = overlayContainerElement.querySelector('.close-without-text')!;
-        expect(button.getAttribute('aria-label')).toBeTruthy();
-      }));
-
-      it('should not have an aria-label if a button has text', fakeAsync(() => {
-        let button = overlayContainerElement.querySelector('[mat-dialog-close]')!;
-        expect(button.getAttribute('aria-label')).toBeFalsy();
-      }));
-
       it('should allow for a user-specified aria-label on the close button', fakeAsync(() => {
         let button = overlayContainerElement.querySelector('.close-with-aria-label')!;
         expect(button.getAttribute('aria-label')).toBe('Best close button ever');
       }));
 
-      it('should always have an aria-label on a mat-icon-button', fakeAsync(() => {
-        let button = overlayContainerElement.querySelector('.close-icon-button')!;
-        expect(button.getAttribute('aria-label')).toBeTruthy();
-      }));
-
       it('should override the "type" attribute of the close button', () => {
         let button = overlayContainerElement.querySelector('button[mat-dialog-close]')!;
 
@@ -1508,8 +1493,6 @@ class PizzaMsg {
     <mat-dialog-content>Lorem ipsum dolor sit amet.</mat-dialog-content>
     <mat-dialog-actions>
       <button mat-dialog-close>Close</button>
-      <button class="close-without-text" mat-dialog-close></button>
-      <button class="close-icon-button" mat-icon-button mat-dialog-close>exit</button>
       <button class="close-with-true" [mat-dialog-close]="true">Close and return true</button>
       <button
         class="close-with-aria-label"
@@ -1528,8 +1511,6 @@ class ContentElementDialog {}
       <mat-dialog-content>Lorem ipsum dolor sit amet.</mat-dialog-content>
       <mat-dialog-actions>
         <button mat-dialog-close>Close</button>
-        <button class="close-without-text" mat-dialog-close></button>
-        <button class="close-icon-button" mat-icon-button mat-dialog-close>exit</button>
         <button class="close-with-true" [mat-dialog-close]="true">Close and return true</button>
         <button
           class="close-with-aria-label"
diff --git a/tools/public_api_guard/lib/dialog.d.ts b/tools/public_api_guard/lib/dialog.d.ts
index 1a5aa83166d0..dfdf61450454 100644
--- a/tools/public_api_guard/lib/dialog.d.ts
+++ b/tools/public_api_guard/lib/dialog.d.ts
@@ -45,7 +45,6 @@ export declare const matDialogAnimations: {
 };
 
 export declare class MatDialogClose implements OnInit, OnChanges {
-    _hasAriaLabel?: boolean;
     _matDialogClose: any;
     ariaLabel: string;
     dialogRef: MatDialogRef<any>;