 <p>You can try using AttachAware and it's attach method. You should implement AttachAware interface in your decorator and/or component.</p> <p>Here's link to Angular.dart docs - <a href="https://docs.angulardart.org/#angular-core-annotation.AttachAware" rel="nofollow">https://docs.angulardart.org/#angular-core-annotation.AttachAware</a></p> <p>To change the styling of a ShadowDom component you can use element.shadowRoot to get the root of your web component. Shadow root is almost like 'document' object. You can use shadow root to get reference to any element and then you can easily modify it by applying styles as needed.</p> <p>You could use something like this.element.shadowRoot.querySelector('[some-attr]').innerHtml = "Modified by decorator" // disclaimer: not tested, but I hope you get the idea.</p>