baldwin made his senior debut for hartlepool united on 17 december 2011 in a 1–0 home defeat against colchester united with caretaker boss micky barron saying "jack came in and was steady. he got on the ball, won his tackles and headers and competed really well. he's been terrific since he came to the club on trial in pre-season." initially playing for the reserve side since the start of the season, baldwin began to establish himself in the hartlepool united's starting eleven, playing in either defensive-midfield and centre-back throughout the 2011–12 season. he went on to make seventeen appearances in his first season and shortly after the end of the 2011–12 season, baldwin committed his future to hartlepool by signing a long-term contract with the club.