The front row, a former pupil at Colston's School in Bristol before he was recruited to Hartpury College by current Warriors Academy Manager Andrew Stanley, has gone on to make 50 appearances for Worcester and is Irish-qualified through his paternal grandfather who was originally from Belfast.
Head Coach Richard Hill said: "Callum is very much the modern-day loose-head prop in that he has good mobility and he has impressed us with his fitness, work-rate, defence, ball carrying and pace.
"Unfortunately he has also created an impression with one or two Irish provinces and he has clear aspirations to play international rugby and qualify to play for the senior side in Ireland.
"We are disappointed to see him leave us, but understand he is a young player who is ambitious in terms of playing international rugby.
"We would never stand in the way of someone who wants to play for their country and have already recruited strongly in this area."