Munster's Pro14 Rainbow Cup commenced with a 27–3 away win against Leinster on 24 April 2021, which was followed by a 38–10 home win against Ulster on 7 May 2021, before Munster's perfect start to the tournament was brought to a halt by a 24–20 home defeat against Connacht on 14 May 2021. The province returned to winning ways with a hard-fought 31–27 win against Cardiff Blues on 28 May 2021, however, Munster's hopes of reaching the final of the tournament were ended when northern pool leaders Benetton were awarded four match points after Covid-19 cases amongst their Welsh opponents Ospreys forced the cancellation of their scheduled fixture, giving the Italian team an unassailable lead at the top of the pool. Munster's final game of the tournament, and the season, was a 54–11 away win against Zebre on 11 June 2021.