The 35-year-old Garrard was removed from the reserve-retired list two weeks ago and placed on the exempt list, meaning he was eligible to practice and attend meetings. The Jets had until 4 p.m. EDT Monday to decide whether to activate him.
Garrard signed with New York in March before leaving because of knee trouble in May. He said he felt healthy after taking the summer to rest and re-considered retirement. Garrard will serve as a backup and mentor to rookie starter Geno Smith.