 <p>I am no expert in Cross Platform Mobile Development (in fact, I was just searching for a cross platform mobile development languages/frameworks), but you could take a look at <a href="https://www.xamarin.com/" rel="nofollow">Xamarin</a>, especially as you have a C# Background.</p> <p>You may also want to take a look at <a href="https://cordova.apache.org/" rel="nofollow">Apache Cordova</a> (and <a href="http://phonegap.com/" rel="nofollow">Adobe Phonegap</a>), they use HTML+CSS+JavaScript.</p> <p>I recently found <a href="https://flutter.io/" rel="nofollow">Flutter</a>, the development language is <a href="https://www.dartlang.org/" rel="nofollow">Dart</a> and it's an early stage OSS project (as of 2016 october) and <a href="https://haxe.org" rel="nofollow">Haxe</a>. They both seem like an active projects, so worth following the progress on GitHub.</p> <p>If I had to choose and I already had skills in C#, I'd go with Xamarin.</p>