McCarthy began writing poetry in the 1960s and was temporarily encouraged after his poem South Boston Sunday was published in a Sunday edition of the Boston Sunday Globe in October 1976. He was disappointed that its publication did not open up any doors for him and concentrated on his career as an information technologist working with banks and insurance companies. In 1993 he took his daughter, Kathleen, on her 17th birthday, to a poetry reading at the Cantab Lounge in Boston, Massachusetts, with the intention of getting her interested in poetry but wound up performing a poem and then returning to perform poetry in competition with other poets (Slam Poetry). This quickly led to some local recognition and he was asked to be part of the competitive Boston Slam Team that would compete in the National Slam Poetry competition in Portland, Oregon in 1996. The competition was filmed by Paul Devlin as part of the documentary SlamNation which was released in 1998 and McCarthy is interviewed and seen performing on stage during the film. He is listed on the official SlamNation official website as a prominently featured poet with a brief bio and picture.