Harrison missed most of last season because of a left knee injury. Manning is back in Indianapolis recovering from surgery to remove an infected bursa sac from his left knee.
Fans chanted Harrison's name and cheered his catches during practice. He has not played in a regular-season game since Oct. 22, though he played in the Colts' playoff loss in January.
Harrison was expected to miss camp due to offseason surgery in January. But coach Tony Dungy announced this week that Harrison was scheduled to practice.
The 35-year-old Harrison has caught 1,042 career passes for 13,944 yards and 123 touchdowns in 12 years with the Colts. Most of those passes have come from Manning.