Born in Cardiff but raised in Glasgow, Evans studied at Glasgow School of Art and exhibited at the Royal Scottish Academy in 1930. In 1931, he was awarded the Haldane Travelling Scholarship and visited Berlin, Copenhagen and Paris. Later that year he won a free place at the Royal College of Art in London. He had an early instinct for abstraction, and painted works with a blend of Surrealist and Cubist elements in secret while at both Glasgow and at the Royal College.
Beginning in 1934 he made frequent trips to Paris, meeting Mondrian, Kandinsky, Giacometti, Max Ernst and William Hayter. He also exhibited with the London Group and at the International Surrealist Exhibition. In 1938 Evans moved to South Africa to take up a teaching post and enlisted in the Signals Company in the South African Army in 1942. In 1946 he moved back to London where his artistic career developed.
He had his first one-man exhibition at the Leicester Galleries in 1949, where he exhibited again in 1952, 1953 and 1955. He continued to exhibit regularly during the 1960s and in 1963 took a studio in St Ives for the summer, where he went annually thereafter. Evans took a post as the exchange artist in residence at the Art Institute of Chicago in 1967, which allowed him to visit New York. Here he met Mark Rothko, Barnett Newman and Robert Motherwell.
On his return to London, Marlborough Fine Art held a one-man exhibition for him entitled 'Events and Abstractions'. The Welsh Arts Council commissioned a triptych of his aquatints the following year and in 1972 the Victoria and Albert Museum held an exhibition of his graphic work.