On his second debut for the club he scored the winning goal in a 2–1 win the Quarter-Final of Football League Trophy tie against York City. Hammill then scored his second goal against Wigan Athletic and Barnsley won 4–2 on penalties after the game was played for 120 minutes in the Semi-Final of Football League Trophy. Following this, Hammill signed a contract with the club. Shortly signing a contract with Barnsley, Hammill scored his first league goal since 2010, in a 3–2 win over Colchester United on 12 December 2015. Three weeks later on 2 January 2016, Hammill scored again, in a 2- 1 in over Millwall and provided two assists, including Sam Winnall's goal, who scored a hat-trick, in a 6–1 win over Rochdale three weeks later on 23 January 2016. After being sidelined over his fitness, Hammill scored on his return on 7 February 2016, in a 3–0 win over Bury. After serving three match ban following a goalless draw against Bury on 23 February 2016, Hammill then scored the winning goal, in the final of Football League Trophy, in a 3–2 win over Oxford United on 3 April 2016. Six days later on 9 April 2016, Hammill scored in a 2–1 loss against Chesterfield. Hammill went on to play a vital role in the League One play-offs promotion to the Championship when he scored two times in three appearance against Walsall in the second leg and the final against Millwall. On his return to Barnsley in his third spell, Hammill made thirty-three appearance and scoring nine times in all competitions.