The team officially announced the hiring on Sunday.
The addition of Henderson, who interviewed for two head coach openings over the last two weeks, fills one of the two key spots on Marinelli's staff. The Lions have yet to hire an offensive coordinator, a position that will be critical, given the ongoing instability at the quarterback position.
One of the men with whom Marinelli wanted to discuss the offensive coordinator spot, former Buffalo Bills coach Mike Mularkey, on Sunday accepted an offer from the Miami Dolphins to run their offense.
Henderson, 48, served as the Jets' coordinator under Herman Edwards for the past two seasons. Under his stewardship, the New York defense statistically ranked No. 7 for the 2004 season, then dropped to 12th in 2005, when the unit suffered a spate of injuries. Although Edwards retained Kansas City coordinator Gunther Cunningham, there was a chance Henderson might have joined his staff, had he not landed a coordinator post.
Marinelli had hoped to hire his son-in-law, Tampa Bay linebackers coach Joe Barry, but the Bucs, as is their policy, denied permission for him to interview for the job, because he has one more season remaining on his contract.
Phil Snow, a defensive assistant with the Lions in 2005, is expected to be retained by the club, although his responsibilities under Marinelli haven't yet been determined. Marinelli is continuing to interview potential staffers at this week's Senior Bowl college all-star game in Mobile, Ala.
In the emotional Henderson, the Lions certainly are getting a coordinator whose passion might match that of Marinelli, a fiery guy. Although Henderson is not a big blitz-quota coach, he preaches an aggressive style, much as Marinelli does, and has experience in the "cover two" scheme Detroit figures to employ under its new head coach.
Henderson entered the league with the Baltimore Ravens in 1999, as secondary coach, and then moved to the Jets in 2004. Before that, he was a college coach for 16 seasons.
Len Pasquarelli is a senior writer for ESPN.com.