After scoring in the pre-season friendly against Rushden & Diamonds, Carrington made his Milton Keynes Dons' debut in the opening game of the season, in a 0–0 draw against Hartlepool United and scored his first league goal for MK Dons against Colchester United two weeks on 22 August 2009. As the season progressed his game developed under the guidance of Ince, and although his starts were limited, he continued to impress when selected, and earned particular praise from the former England midfielder after scoring twice in the 3–1 win against Southend United on 20 February 2010. Carrington then scored his fourth goal for the club on 6 March 2010, in a 1–0 win over Leyton Orient and finished the 2009–10 season, making nineteen appearance and scoring two times.