Crawford took to Twitter to show himself signing the paperwork.
The Cowboys and Crawford's agent, Todd France, had been in discussions about a deal, with the process picking up in recent days. The hope had been to get a deal done before Sunday night's season opener or soon thereafter.
"He represents everything that we want to wear the star," executive vice president Stephen Jones said Friday. "He's a really solid player on the field and plays the way we want to play the game and even a better guy off the field. We're working hard to ensure that he'll be there."
Crawford was scheduled to be an unrestricted free agent after the season and was set to make a $675,000 base salary on the final year of his $2.74 million rookie deal.
"I think everybody knows how much I love Dallas, love this team, love this organization, love the ownership, my teammates," Crawford said.
A third-round pick in 2012, Crawford missed the 2013 season with a torn Achilles but flourished in a move to the under tackle in Rod Marinelli's 4-3 scheme in 2014. He finished with three sacks but was second on the team in quarterback hurries (29) and second among defensive linemen in tackles (37).
Crawford was named the team's Ed Block Courage Award winner after the 2014 season for his comeback from the torn Achilles. For his career he has been credited with 70 tackles, three sacks, four tackles for loss, 34 quarterback pressures, one pass breakup and one forced fumble.
"He's really shown us everything that we need to see to know that he can be one of the elite under tackles in this league," Jones said.