Two years later in 1943, Mulcahy took over as first-choice goalkeeper with the Cork senior team. A 2–13 to 3–8 defeat of Waterford that year gave him his first Munster medal. He later lined out in his first All-Ireland decider with Antrim becoming the first Ulster side to qualify for a final. Unfortunately, the occasion got to the Glensmen as Cork built up an unassailable 3–11 to 0–2 half-time lead. The final score of 5–16 to 0–4 gave Cork their second-ever hat-trick of All-Ireland titles while it also gave Mulcahy a first All-Ireland medal.