Deri Tomos was brought up in Cardiff and educated at Bryntaf Welsh School and then Cardiff Boys High School. He studied Biochemistry at King's College, Cambridge ensuring a doctorate in plant biochemistry. After completing his doctorate he spent a time as a research fellow at Bangor University and was appointed lecturer in 1985. Within ten years he received a personal chair at the university.
While pursuing a bright academic career he has spent years making science more accecable, particularly through the medium of Welsh. He has been a prolific broadcaster on radio and television, writing a regular column to Barn for many years, and he is a leading member of the Cymdeithas Wyddonol Genedlaethol’. He was awarded the National Eisteddfod's science Medal in 2017.
For over thirty years, Deri Tomos has pioneered Welsh-medium teaching and was central to developments in biochemistry and biomedicine. He was a leading and active member of the Coleg Cymraeg’s Academic Board from its inception in 2011 until his retirement last year.