|First Appearance||"Mystery Meat" April 3, 2004|
|Hair Color||Black and Gray|
|Relatives||Maddie (spouse), Danny (son), Jazz (daughter)|
|Residence||Fenton Works, Amity Park|
Jack is Danny and Jazz's father. He is a professional jumpsuit-wearing ghost hunter who make it their hobby and goal to study and eradicate "all things ectoplasmic." Jack is the most obsessed with ghost-hunting. He jumps into action before thinking and can make a bad situation even worse. While he can often act clumsy and incompetent, he holds a great deal of courage and is an adequate fighter, at one point clashing toe-and-toe against Vlad Plasmius and defeating him, much to the latter's surprise and embarrassment. He is a genius who has a good amount of technical knowledge, and is able to conjure up working ghost gadgets and defense systems built all around the Fenton household. He also has a maturity and seriousness that few people recognize and can get serious and show great skill when danger threatens his loved ones.
Jack appears as a non-playable character in Nicktoons Unite!. He was first briefly seen in the background when the heroes first arrive at Amity Park. He was hypnotized and couldn't do anything while he was being held captive by Vlad. When the heroes battle Vlad, Danny has to take over Jack's body so he can break Vlad's ghost shield and hit him.