Henderson, currently a free agent, is seeking $3.3 million in compensatory damages -- the amount of his unpaid 2016 salary, plus his non-guaranteed 2017 salary. In February, the Jets declined to exercise his 2017 option for $2.25 million. Henderson, 31, also is seeking punitive damages.
His New Jersey-based attorney, Lawrence Lavigne, sent a notification letter, dated Sept. 14, to Jets chairman and CEO Christopher Johnson. The letter said he would file the lawsuit in New Jersey Superior Court on Friday if the two sides can't agree to a private settlement.
In an interview with ESPN, Lavigne said he hasn't heard back from the Jets.
Henderson's case is rooted in the team's decision to place him on the non-football injury list last Oct. 22. Lavigne said the Jets didn't pay the remaining portion of Henderson's salary ($580,871), plus a $250,000 roster bonus.
Lavigne acknowledged the NFL's collective bargaining agreement permits teams to withhold salary for players on the NFI list, but he said the Jets violated New Jersey law by never giving a reason.
Henderson, a starting linebacker, never played again last season. Publicly, the Jets didn't give a reason for the decision. Henderson filed a grievance through the NFLPA in June, at which time the Jets claimed he was "not fit" to play without giving specifics, Lavigne said.
The lawsuit claims the team's silence, coupled with Henderson's history of alcohol problems, fueled rumors that he had relapsed, causing potential suitors to shy away.
"Our argument is they did everything wrong, so they either destroyed a career by remaining silent or they wrongfully terminated him," Lavigne said.
A Jets spokesman declined comment.
Lavigne maintained that Henderson, who had two DUI arrests while playing for the Minnesota Vikings, had no alcohol issues with the Jets.
Lavigne said his client overslept and was late for a meeting about 10 days before he was placed on the NFI list. That, he said, was due to a side effect from a team-prescribed medication for his bipolar disorder. He said Henderson explained that to a Jets official.
"He said, 'Look, I took these pills last night that your doctor gave me and I woke up a little later this morning.' And that was that," said Lavigne, claiming the bipolar disorder didn't affect Henderson's ability to perform.
When the season ended, the Jets cut off Henderson's medication "cold turkey," his agent, Jim Chapman, said.
Chapman speculated the Jets didn't want Henderson because they felt first-round pick Darron Lee was ready to take his position. Henderson also got into an argument with receiver Brandon Marshall at practice. He confronted Marshall after the wide receiver angrily punted a ball over the fence at practice. That, Chapman suspected, may have hurt Henderson's standing with the team.
"Erin feels like the Jets never had his back," Chapman said. "This has been devastating to him."