Melton, who played each of his first four seasons with the Chicago Bears, announced the news via Twitter at 7:18 p.m. Dallas time.
As of 7:49, the actual paperwork in Melton's deal wasn't completed due to the "complicated nature" of the contract, according to team sources.
FOX Sports 1 NFL Insider Mike Garafolo reports that Melton's contract will initially be a one-year deal, but an additional three years will trigger if he remains on the roster at the start of the next league year.
Thank you chicago for the best 5 years of my life!.... I can't wait to begin the next chapter of my life... With a star on my helmet.
Both sides finished Monday's day-and-night meet-and-recruit session feeling like "this is a good fit" -- the term used by multiple involved parties. And maybe the deal-closer was Melton's dinner with Rod Marinelli, Dallas' defensive coordinator who held the same role with the Bears when he mentored Melton to stardom.
The "complications" in the contract could have something to do with incentives based on the fact that Melton, 27, played only three games last season before suffering a torn left ACL. Cowboys doctors, however, have apparently given him clearance and another source said Melton is "90-percent" recovered and should be fine for 2014.
Melton, who received the franchise designation in 2013, paying him $8.45 million, will replace Jason Hatcher — who left to join the Redskins — in the Dallas defense. Melton, a Grapevine and University of Texas product, was coveted by the Seahawks, Vikings, Rams and others. He was named to the Pro Bowl in 2012 and has 15.5 career sacks.
Melton is the third defensive linemen the Cowboys have added in free agency, joining journeyman end Jeremy Mincey and tackle Terrell McClain. The Cowboys also met with end Jared Allen today and continue to explore the return of end Anthony Spencer, who is coming off microfracture surgery on his knee.