Cadwaladr first appears in the historical record in 1136, when following the killing of the lord of Ceredigion, Richard Fitz Gilbert de Clare, he accompanied his brother Owain Gwynedd in an invasion of Ceredigion. They captured five castles in the north of Ceredigion then later in the year launched a second invasion, inflicting a heavy defeat on the Normans at the Battle of Crug Mawr, just outside Cardigan. In 1137 they captured Carmarthen. He later married Richard Fitz Gilbert de Clare's daughter Alice (Adelize) de Clare and had issue with her.