He began his NFL career in 1972 after coaching high school and college football.
He spent eight years (1989–97) with the New York Jets, beginning as a defensive assistant coach and advancing to director of player administration, where he negotiated contracts and managed the team's salary cap.
He currently co-hosts on SiriusXM NFL Radio's Movin' the Chains with Jim Miller.
He is the author of Take Your Eye Off the Ball: How to Watch Football by Knowing Where to Look (2010), along with David Seigerman.
[citation needed] In the 2017 video game Madden NFL 18's story mode Longshot, Kirwan and Jim Miller co-host a fictional show called Real Football.