Munster moved to bring Healy into their academy immediately after he had completed his leaving cert,[4] with Healy joining ahead of the 2018–19 season.[5] He made five appearances for Munster A during the 2018–19 Celtic Cup, scoring 19 points.[1]
Healy made his senior competitive debut for Munster in their 2019–20 Pro14 round 7 fixture against Edinburgh on 29 November 2019, starting at fly-half and scoring 11 points in the provinces 18–16 defeat.[6] He made his European debut for Munster in their final pool 4 fixture of the 2019–20 Champions Cup against Welsh side Ospreys on 19 January 2020.[7]
Healy came off the bench to replace starting fly-half JJ Hanrahan in Munster's opening 2020–21 Pro14 fixture away to Welsh side Scarlets on 3 October 2020, scoring ten points of the kicking tee, including the conversion of Kevin O'Byrne's 77th minute try to level the scores with just minutes remaining of the game, before scoring a 50-metre penalty in the 81st minute to earn a 30–27 win for Munster.[8]
One week later, Healy started for Munster in their match against Edinburgh, scoring six of his seven penalties and converting CJ Stander's 76th minute try to earn a 25–23 win for the province.[9] He joined the Munster senior squad on a one-year contract for the 2021–22 season.[10] Healy scored his first try for Munster in their 31–17 win against Italian side Benetton in round 16 of the 2020–21 Pro14 on 19 March 2021.[11] For his performances throughout the 2020–21 season, Healy was awarded the John McCarthy Award for Academy Player of the Year.[12]
Healy signed a one-year contract extension in January 2022.[13] He started in Munster's historic 28–14 win against a South Africa XV in Páirc Uí Chaoimh on 10 November 2022, scoring all four of his attempted conversions for eight points and a 100% kicking record during the match.[14] Healy scored a 79th minute try and converted it to earn a 15–14 away win against Ulster in round 11 of the 2022–23 United Rugby Championship on 1 January 2023, a result that had seemed unlikely for much of the game.[15]
Healy is Scottish-qualified through his maternal grandparents, and in 2020 the Scottish Rugby Union attempted to persuade him to join Glasgow Warriors. Though Healy rejected that offer and signed a one-year contract extension with Munster, Scotland head coach Gregor Townsend retained interest in him,[24] and Healy would subsequently agree to join Edinburgh on a two-year contract from the 2023–24 season.[18] He was selected in the Scotland squad for the 2023 Six Nations Championship following the announcement of his transfer to Edinburgh and an injury to fly-half Adam Hastings,[25] and made his international debut for Scotland in their final fixture of the tournament against Italy on 18 March, featuring as a replacement during the second-half of their 26–14 home win.[26]