 <p>You need to specify the encoding in the HTML file of the Polymer element.</p> <pre><code>&lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8"&gt; </code></pre> <p>See also <a href="http://stackoverflow.com/questions/22790895/i-have-greek-text-on-a-string-in-dart-using-polymer-why-is-it-displayed-wrongly">I have greek text on a String in Dart using Polymer, why is it displayed wrongly on the browser?</a></p>