Index: src/wp-admin/js/theme.js
===================================================================
--- src/wp-admin/js/theme.js	(revision 27804)
+++ src/wp-admin/js/theme.js	(working copy)
@@ -332,6 +332,12 @@
 
 		preview.render();
 		$( 'div.wrap' ).append( preview.el );
+
+		// Set focused theme to current element
+		themes.focusedTheme = this.$el;
+
+		// set focus in the preview
+		$( '.close-full-overlay' ).focus();
 	}
 });
 
@@ -528,6 +534,11 @@
 			$( 'body' ).removeClass( 'theme-installer-active full-overlay-active' );
 		});
 
+		// Return focus to the theme div
+		if ( themes.focusedTheme ) {
+			themes.focusedTheme.focus();
+		}
+
 		themes.router.navigate( themes.router.baseUrl( '' ) );
 		return false;
 	},