Garner, 37, has signed a six-month contract having scored five goals in 17 appearances last season, including one from the penalty spot in the 3-2 National League promotion final win over Southend United at Wembley earlier this month.
Hammond, 22, arrived from Nottingham Forest in January 2024, and featured in eight of Oldham’s National League games last season. He has signed a two-year contract.
Sutton has also agreed a two-year deal having come through the Latics academy, with the 22-year-old making more than 50 appearances.
“Each of them brings something important to the squad, Oli with his energy and potential, Joe with his experience and leadership, and Will with his strength and commitment,” Oldham boss Micky Mellon told the club website., external
Oldham open their first EFL season in three years at MK Dons on 2 August.