He made his debut straight out of the minor ranks in 1963 and immediately became a regular fixture at midfield. After losing the championship decider to Glen Rovers in 1964, "the Barr's" were back for a second successive final the following year. University College Cork provided the opposition, however, a youthful St. Finbarr's team powered to a 6–8 to 2–6 victory. It was McCarthy's first championship medal. A subsequent 3–12 to 2–3 trouncing of Waterford's Mount Sion gave him a Munster medal.