St Patrick's Athletic
2016 season
In January 2016, Markey went on trial with Scottish Premier League champions Celtic, scoring in a trial game vs Kilmarnock.[10][11] Nothing came of the move as Markey decided to take up the scholarship offer between St Pat's and NUI Maynooth, taking up a degree in finance at the college.[12] To secure the degree, Markey would have to get the necessary points on his Leaving Cert, which he sat in June 2016. With the importance of his studies having to come before his football, the first half of 2016 turned out to be less productive for Markey as he made 7 league appearances and two league cup appearances that season (all 9 coming on from the substitutes bench) as Pat's won the 2016 League Cup.[13]
2018 season
Markey's shirt number changed again to number 15 ahead of the 2018 season. He started the season out of the starting 11, having to come off the bench in the first few games but regained his spot in the attacking midfielder role in the 0–0 draw with Dundalk.[19] He scored his first senior goal on 15 May 2018 in a 5–2 win over Derry City at Richmond Park.[20] His next goal came on 10 August when he opened the scoring in a 5–0 win over Inchicore Athletic in the FAI Cup first round.[21] The season proved to be a disappointment for his side as they missed out on European football once again, which saw the departure of Liam Buckley as manager. On a personal level for Markey however, the season was another big step in his development, making 36 appearances and scoring 2 goals.[9]
2019 season
Following on from a full season as a regular starter, Markey was given the number 8 shirt for the 2019 season.[22] Markey had to wait until 15 March 2019 for his first appearance of the season under new manager Harry Kenny, coming on as a substitute in a 2–0 loss away to Waterford.[23] He had to wait a month for his next appearance, making his first start of the season in a 1–1 draw away to Cork City.[24] From then on he remained a mainstay in the team and on 17 May he scored his first goal of the season, opening the scoring in the Dublin derby against Bohemians with a looping header over James Talbot in the 40th minute.[25] Markey saw his first taste of European football when he came off the bench away to IFK Norrköping of Sweden in a UEFA Europa League Qualifier, assisting Conor Clifford's goal in a 2–1 loss for Pat's.[26] With the side struggling in front of goal, manager Harry Kenny was replaced by Stephen O'Donnell following a shock cup exit to UCD in late August and in O'Donnell's first match, Markey scored in a 2–1 win away to Finn Harps on 6 September 2019.[27] He finished the season with 30 appearances and 2 goals in all competitions.[9]
2020 season
The 2020 season was a difficult one for Markey as the league season was halved due to the Coronavirus pandemic which also saw the League Cup and Leinster Senior Cup abandoned. As a result of this, Markey struggled for game time, playing in 11 of the club's 19 league and cup games, starting just 3 of them as his side finished in 6th place, missing out on European football on the final day of the season.[28] Markey left the club at the end of the season, having made 116 appearances and scoring 4 goals for the Saints.[28]
Drogheda United
On 29 November 2020, Markey signed for newly promoted Drogheda United ahead of the 2021 season.[29] He made his debut in the opening game of the season, a 1–0 win at home to Waterford on 19 March 2021.[30] His first goal for the club came on 8 May, opening the scoring in a 7–0 win away to Waterford at the RSC as the home side fielded their under-19 squad due to a COVID-19 outbreak in the first team squad.[31] Markey scored the second goal in a 3-1 home victory against Finn Harps on 2 July, and netted again on the penultimate day of the season at home against Longford Town. He finished the season with 3 goals in 36 appearances in all competitions as his side finished in a respectable 7th place.[28] On 10 December 2021, Markey signed a new contract with the club for the 2022 season.[32][33] On 14 March 2022, he sustained a broken foot in a 2–0 defeat to Derry City at the Ryan McBride Brandywell Stadium on just his 5th appearance of the season, with the injury requiring surgery.[34] Markey scored his first goal of the season on 29 July 2022 in a 5–1 win over Athlone Town in the FAI Cup.[35] He had to wait until the final day of the season for his first league goal of the year, opening the scoring in a 2–0 win over relegated Finn Harps on 6 November 2022.[36] Markey finished his second season at the club with 2 goals in 26 appearances in all competitions.[28] On 9 December 2022 Markey signed a new deal with Drogheda for the 2023 season despite reported interest from Bohemians.[37] On 10 February, he scored a brace against Athlone Town which saw Drogheda advance to the quarter finals of the Leinster Senior Cup. On 9 June, he scored the winning goal in injury time in a 2-1 league victory over his former club St. Patrick's Athletic. Markey played in 33 of Drogheda's 36 league games, as the club avoided relegation and climbed up to 7th place. On 10 December 2023, he signed a new contract with the club.[38] On 10 November 2024, he was part of the stating 11 in the 2024 FAI Cup final as his side defeated Derry City 2–0 in the Aviva Stadium.[39] On 13 November 2025, Drogheda confirmed that Markey would be departing at the end of his contract, despite efforts to extend his contract, having scored 13 goals in 179 appearances in his 5 seasons with the club.[40]