[1][2] Garth comes from a cricketing family, with his father Jonathan, mother Anne-Marie McDonald, and his sister Kim all representing Ireland at an international level.
[4] Prior to his List A debut, he was named in Ireland's squad for the 2018 Under-19 Cricket World Cup.
[5] He made his first-class cricket debut for Ireland A against Sri Lanka A on 5 January 2019.
[8][9] Following his inclusion in the training squad, Garth said he was "surprised but delighted" to be named in the team.
[10] In February 2021, Garth was named in the Ireland Wolves' squad for their tour to Bangladesh.