Born in Truro, Nova Scotia, as a teenager Holmes taught himself to draw by copying such artists as Wally Wood and Will Eisner. He moved to Vancouver in 1969 and found work as an illustrator at The Georgia Straight, a weekly alternative newspaper. He drew numerous covers for the publication and eventually created the Harold Hedd comic strip, which ran in the paper during the early 1970s. Described by writer Dana Larsen as Holmes's "most well known cartoon creation", the strip was sufficiently popular to have two oversized comic magazine volumes, The Adventures of Harold Hedd, published by Last Gasp in 1972 and 1973.
Holmes's work appeared in such underground comics titles as White Lunch Comix, Fog City Comix, Slow Death, and Death Rattle. He also had some artwork published in Harvey Kurtzman's Help!. In the early 1980s, he provided illustrations for several stories in Pacific Comics's Alien Worlds and Twisted Tales. Later in that decade, he and his wife and three children moved to Lasqueti Island, where he concentrated on oil painting until the end of his life.