O'Connell's only NFL action came in mop-up duty in 2008, including the fourth quarter in the Dolphins' 38-13 victory at New England in September.
O'Connell was claimed off waivers by Detroit after being let go by the Patriots and later was traded to the Jets for a seventh-round pick.
Because of a torn labrum, O'Connell didn't play at all last season.
Along with O'Connell's signing, the Dolphins also released quarterback Tom Brandstater.
O'Connell's arrival doesn't change much in the big picture at quarterback, where Henne will be the starter unless he gets badly outplayed by Matt Moore this summer.