It depends on what framework you are running you website. Not sure how far back 2012 will support .net versions. It might work if you managed it to work on 2010. But I would sugest you try to upgrade or build a new website, much more fun :)
I have an Episerver 4.6 solution, will this work if upgraded to a Visual 2012 solution?
Is it possible to develop an EPiServer 4.61 site on Visual Studio 2012?
Any special configuration needed?