The Cowboys fully guaranteed the three-year, $1.65 million deal, a source told ESPN NFL Insider Adam Schefter.
Because Collins did not have his first-round moment, as owner Jerry Jones called it, the Cowboys went the unorthodox route of having a press conference for an undrafted free agent "because this is not your typical undrafted free agent," Jones said.
"I got a call from Mr. Jones a couple nights ago, late around 11 o'clock," Collins said. "We had a long conversation, man and that was the first time I really felt like somebody seeing me for who I am. Somebody understood the guy, that I went back to school my senior year because I wanted to be something special. I wanted to do everything I had to do to put myself in a great position and I sat down with him. He believed in me, he trusted me and I couldn't have asked for anything else. I couldn't be in a greater situation. I couldn't be in a greater place. I just want to thank Mr. Jones, his family this organization and everybody that is standing behind me because I guarantee you this: I'm going to give this organization everything I have and more. This is going to be the best offensive line in NFL history. Mark my words."
Collins, who also will receive a $21,000 signing bonus, was viewed as a first-round pick entering last week's draft but went undrafted when his name was linked to an investigation into the murder of his pregnant former girlfriend.
Collins was questioned by Baton Rouge, Louisiana, investigators about Brittney Mills' death on April 24. Although he is not a suspect, he has yet to be fully cleared. Collins was one of the best offensive linemen available in last week's draft, but teams were unwilling to select him because of the uncertainty of his involvement.
A paternity test showed Collins was not the father of Mills' child. He also passed a polygraph test, according to ESPN's Josina Anderson. Mills' child survived the shooting but died a week later after being born in the hospital.
Collins said he has fully cooperated with the police in the investigation but could not comment further. Jones said the Cowboys did their own background work.
"He left one thing out: He had nothing to do with it," said Jones, who was emotional as Collins spoke during the press conference, as he wiped away a tear.
Teams are not allowed to meet with undrafted players at their school or residence, which led to the meeting with the Cowboys in Dallas. Collins also met with Buffalo Bills coach Rex Ryan, and a number of Collins' former LSU teammates on the Miami Dolphins attempted to recruit him, as well.
On Wednesday night, Collins had dinner at Jones' Highland Park home that was also attended by Tony Romo, Jason Witten, Tyron Smith, Travis Frederick and Zack Martin as well as executive vice president Stephen Jones, coach Jason Garrett and offensive line coach Frank Pollack.
"From the moment you get there, you got the leaders of the team that are there -- guys like Tyron Smith, a guy who hosted me on my visit when I went to USC," Collins said. "I looked up to him. When I was in high school, I used to watch him play all of the time. When he got drafted, I was like, 'Wow, I know that guy.' And guys like Tony Romo, you watch him play week in and week out. You watch how, at times, people try to criticize him, but he never once folded, he never once blinked. He stands right back up in the light of adversity. Those are guys who have been faced with challenges throughout life. I fit right in with those guys. ... I am part of something special. This is going to be a powerful thing, man."
League rules prevent Collins from taking part in the team's rookie minicamp, which starts Friday.
While Collins started his final two years at LSU at left tackle, he projects more as a guard in the NFL. He started 13 games at left guard his sophomore year.
Ronald Leary has been the Cowboys' left guard the past two seasons, starting every game in which he has been active.
Already considered one of the best lines -- if not the best line -- in the NFL, the addition of Collins to a group that includes first-rounders Tyron Smith, Travis Frederick and Zack Martin, as well as steady right tackle Doug Free, would further solidify the Cowboys' front.
Collins is the third high-profile addition for the Cowboys at less than full price. The Cowboys signed Greg Hardy to a one-year deal in free agency, in part because teams did not want to deal with Hardy's domestic violence issues. He subsequently received a 10-game suspension, which he is appealing. Last week, the Cowboys were able to select Randy Gregory in the second round of the draft. He was pegged as a high first-round pick at the start of the draft process but a failed drug test at the NFL scouting combine, and other issues scared teams off.