Born in Neath, she lived in Porthcawl and then Carmarthen. Kezia trained at RADA, graduating in summer 2004. She first took roles in various theatre productions. She made her first television appearance in ITV1's The Capgras Tide, before starring in the 2009 BBC Wales commissioned, Tony Jordan produced hospital drama Crash as Dr Cath Llewelyn. She voices Nilin in the video game Remember Me.