Club

Larkin played his club hurling with the famous James Stephens club in Kilkenny and enjoyed much success. He won his first senior county title in 1935. Two years later Larkin was captain of the club as he captured a second county title with 'the village.’

Inter-county

Larkin first came to prominence on the inter-county scene for Kilkenny in the early 1930s. He won his first Leinster title in 1931 following a victory over Laois in the provincial final. Larkin later lined out in his first All-Ireland final with Cork providing the opposition. The low-scoring game ended in a draw – 1–6 apiece. Four weeks later the two times met again for the replay. In a similar pattern Cork took the lead at half-time, however, Kilkenny fought back to equalise. At the final whistle both sides finished with 2–5. The third game of the series took place in the first week of November, however, on this occasion there would be a winner as Cork sealed the victory by 5–8 to 3–4.

In 1932 Larkin captured a second Leinster title as Dublin were defeated in the provincial final. The subsequent All-Ireland final saw Kilkenny take on Clare. It was the first ever meeting of these two teams in the history of the championship. In a close and exciting match Kilkenny took the lead thanks to goals by Matty Power, Lory Meagher and Martin White. Clare fought back, however, Kilkenny hung on to win the game by 3–3 to 2–3 giving Larkin his first All-Ireland medal.

Larkin won a National Hurling League medal at the start of 1933 before helping Kilkenny to retain their provincial dominance in with a defeat of Dublin, giving Larkin a third Leinster medal. A defeat of Galway in the next game set up an All-Ireland final meeting with Limerick. In another tight game Kilkenny sealed the victory with a 1–7 to 0–6 score line giving Larkin his second consecutive All-Ireland title. Kilkenny lost their provincial title in 1934, however, Power won a fourth Leinster medal in 1935. The All-Ireland final saw Kilkenny take on Limerick for the second time in three years. Once again the match was a close one, however, Kilkenny clung on and won by a single point – 2–5 to 2–4. It was Larkin's third victory in an All-Ireland final.

In 1936 Larkin was appointed captain of the Kilkenny team. That year he guided his team to another Leinster final victory over Laois, his fifth winners' medal in all, before lining out in yet another All-Ireland final. Once again, the two outstanding teams of the decade, Kilkenny and Limerick, were paired together in the championship decider. Limerick were coming into their prime at this stage and gained revenge for the defeats of 1933 and 1935 by trouncing 'the Cats' on a score line of 5–6 to 1–5.

Kilkenny bounced back in 1937 with Larkin adding a sixth Leinster title to his collection. The All-Ireland final pitted Kilkenny against Tipperary in the unusual venue of FitzGerald Stadium in Killarney. 'The Cats' were definitely on a downward spiral by this stage as they were walloped by 3–11 to 0–3.

Larkin was appointed captain of Kilkenny for the second time in 1938, however, Dublin accounted for his team in the Leinster final. In 1939 'the Cats' reclaimed their provincial crown with a victory over All-Ireland champions Dublin. It was Larkin's seventh provincial medal of the decade. The subsequent All-Ireland final against Cork has gone down in history as the famous 'thunder and lightning' final when a huge downpour interrupted play. In the end victory went to Kilkenny by a single point. It was not the last time that 'the Cats' would defeat 'the Rebels' by a single point in a final. It was Larkin's fourth All-Ireland medal.

In 1940 Larkin added an eighth Leinster medal to his collection after another defeat of Dublin. The All-Ireland final saw Kilkenny and Limerick, the two dominant teams of the last decade, take to the field for one final game. Kilkenny had peaked in the final the year before while Limerick were now reaching their prime. A 3–7 to 1–7 defeat for Kilkenny resulted in Larkin ending up on the losing side for the fourth time.

An outbreak of foot-and-mouth disease in the county hampered Kilkenny's championship hopes for the next few seasons. In spite of this the team bounced back in 1943 with Larkin adding a ninth Leinster medal to his already impressive collection. The subsequent All-Ireland semi-final provided what was regarded as the time as the biggest shock in the history of the championship. Antrim had defeated Galway in the All-Ireland quarter-final in, what was described as, a fluke. Antrim proved that their victory was far from lucky as they defeated Larkin's side in the subsequent semi-final. This marked one of Larkin's last appearances for Kilkenny as he retired from inter-county hurling shortly after.

Provincial

Larkin also lined out with Leinster in the early years of the inter-provincial hurling championship. He first lined out for his province in 1932 and captured his first Railway Cup medal following a victory over Munster. Larkin won a second Railway Cup title in 1933; however, Munster reclaimed the title in 1934 and 1935. In 1936 Larkin was captain of Leinster as he collected his third Railway Cup memento. It was his last medal with his province; however, he continued playing until 1939.