Twomey joined the Courcey Rovers club at a young age and played in all grades at juvenile and underage levels. On 10 October 2015, he lined out at left wing-forward when Courcey Rovers suffered a 1-14 to 2-10 defeat by Ahan Gaels in the Minor A Championship final.[citation needed]
On 22 April 2018, Twomey made his first appearance for the club's top adult team in the Premier Intermediate Championship. He scored a hat-trick of goals in the 3-18 to 0-19 defeat of Inniscarra.[2] On 21 October 2018, Twomey scored two points from left corner-forward when Courcey Rovers drew 0-12 to 1-09 with Charleville in the final.[3] He was switched to right wing-forward for the replay a week later but ended on the losing side after a 0-15 to 0-14 defeat.[4] Three years later on the 27 November 2021 Twomeys side got to another Premier Intermediate Final played in Pairc Uí Choaimh in a incredible comeback from 8 points down against Castlelyons to go on to win 1-19 to 1-18 with Twomey scoring 2 points to earn Twomey a championship medal.
Twomeys side went on to get into the Munster Intermediate Final in the same year after a late rally of points to send it to extra time to go on and lose to Kilmoyley of Kerry 0-24 to 0-21 with Twomey scoring 1 point played in the Gaelic Grounds.
Twomeys side yet again got to another final in the 2022 Senior A final just after winning Premier Intermediate year prior but lost to a very talented Fr. O'Neill's 0-20 to 2-12 played in Pairc Uí Choaimh with Twomey being held scoreless.
Cork
Under-17 and under-20
Twomey first lined out for Cork as a member of the under-17 team during the 2017 Munster Championship. He made his first appearance for the team at midfield on 11 April in a 0-16 to 0-06 defeat of Limerick.[5] On 25 April 2017, Twomey won a Munster Championship medal after a 3-13 to 1-12 defeat of Waterford in the final. He was again at midfield for Cork's 1-19 to 1-17 All-Ireland final defeat of Dublin at Croke Park on 6 August 2017.[6]
On 3 July 2019, Twomey made his first appearance for Cork's inaugural under-20 team in the Munster Championship. He came on as a 39th-minute substitute for Simon Kennefick in the 1-20 to 0-16 defeat of Limerick.[7] On 23 July 2019, Twomey top-scored for Cork with 1-02 from left wing-forward in a 3-15 to 2-17 defeat by Tipperary in the Munster final.[8] He was selected at right wing-forward when Cork faced Tipperary for a second time in the All-Ireland final on 24 August 2019, however, he ended the game on the losing side after a 5-17 to 1-18 defeat.[9]
Senior
On 20 December 2019, Twomey made his first appearance for the Cork senior team when he was selected at left wing-forward for Cork's Munster League game against Kerry. He scored four points from play in the 1-27 to 0-11 victory.[10] Twomey made his first National League appearance on 26 January 2020 when he was introduced as a 60th-minute substitute for Conor Lehane in a 1-24 to 3-17 first round defeat by Waterford.[11]