Born in Newry Street, Frederick Edward McWilliam was the son of Dr William McWilliam, the local GP. Growing up in Banbridge had a great influence on his work. He made references to furniture makers such as Carson the Cooper and Proctors in his letters to his friend, Marjorie Burnett.

He studied for a time at the Slade School of Art in London, where he was later to end up teaching. During the first year of the Second World War he joined the Royal Air Force and was stationed in England were he was engaged in interpreting aerial reconnaissance photographs. Even during this time he was still able to exhibit and teach art.

In 1964 he was awarded an Honorary D. Litt. from the Queen's University Belfast. In 1966 he was awarded a C.B.E. and in 1971 he won the Oireachtas Gold Medal.