Poynton started off playing with East Meath United, before moving to Dundalk aged 15 in August 2013. He was fast tracked to the club's under 19's team and continued to impress at that level despite playing 3 years above his age group. He became the youngest ever player to sign a professional contract with Dundalk aged just 16 years 5 months old, on 14 February 2014, despite interest from Middlesbrough and Hibernians.
On 22 May 2015, Poynton made his League of Ireland debut, coming on as a substitute for Ronan Finn in a 2–0 win away to St Patrick's Athletic. He made a total of 8 appearances in all competitions, including 3 in the Leinster Senior Cup, one of which being in the final as his side won the competition by beating Shamrock Rovers 3–1 at Oriel Park. Poynton also picked up a league winners medal as Dundalk retained their League of Ireland Premier Division title as well as winning the 2015 FAI Cup. He signed a new 2-year contract on 5 November 2015.
2017 was the first season Poynton was finished up playing Under 19's football with Dundalk alongside senior football and with Dundalk chasing their fourth league title in a row, they opted to send Poynton out on loan in order to get game time at first team level. He was loaned out to Bohemians until the summer ahead of the season. Poynton's impressive form saw Bohs extend the loan deal until the end of the season. He made 27 appearances for Bohs, scoring 5 goals in his first full season as a senior player.
Poynton returned to Dundalk for the 2018 season, signing a new contract with the club on 8 January 2018. 2018 proved to be a difficult one for Poynton as he struggled to break into the starting eleven ahead of Robbie Benson, Stephen O'Donnell and Chris Shields. He made 11 appearances in all competitions as Dundalk smashed many records to retain their league title and also completing the double by beating Cork City to win the FAI Cup at the Aviva Stadium.
St Patrick's Athletic
On 29 November 2018, it was announced that Poynton had signed for Dublin club St Patrick's Athletic, becoming new manager Harry Kenny's fifth new signing. Poynton made his debut on 18 February in a 3–0 Leinster Senior Cup win over Wexford at Richmond Park. It was announced on 23 February 2019 that Poynton had left the club by mutual consent, having not made the bench in the Saints first two league games of the season, with Poynton facing an uphill battle for first team action as the club had signed Chris Forrester and Rhys McCabe in his position after he had signed.
Waterford
Waterford announced the signing of Poynton the same day it was announced he has left St Patrick's Athletic, with Poynton seeking more first team action.
Shelbourne
Shelbourne announced the signing of Poynton for the 2020 season.
International career
Poynton has played at underage level for Ireland right up from under 16 to under 19 levels as well as competing at Universities International level, captaining his team at all levels. On 19 March 2017, Poynton was named Republic of Ireland U19Player of the Year for 2016 after his excellent performances.
Career statistics
Professional appearances – correct as of 27 February 2020.
Honours
Club
;Dundalk
League of Ireland Premier Division : 2014, 2015, 2016, 2018
