Collins checked in with 10:28 to go in the second quarter and received a round of applause from the Staples Center crowd.
"Sometimes in life something happens and there's an opportunity," he said shortly before taking on the Los Angeles Lakers Sunday night. "I'm very thankful for this opportunity. That's why I work so hard, why I train the way I do so that when I do have an opportunity physically I'm not worried about my conditioning or cardio or anything along those lines."
"The decision to sign Jason was a basketball decision," Nets general manager Billy King said in a statement. "We needed to increase our depth inside, and with his experience and size, we felt he was the right choice for a 10-day contract."
The Nets tweeted out a picture of Collins signing his contract.
Collins will wear No. 98 for the Nets, but was unable to wear it Sunday because it was not available in time for the game against the Lakers, so he wore No. 46 instead.
Collins' choice of the No. 98 is in honor of Matthew Shepard, a University of Wyoming student who died in a notorious anti-gay hate crime in 1998. Collins has worn the jersey number with both the Celtics and Wizards.
The Nets moved quickly to make the historic signing of the 35-year-old free agent center to have another big body available against the Lakers. Brooklyn had been contemplating signing Collins for the past week and the need for Collins became greater after the Nets dealt rebounding specialist Reggie Evans to the Sacramento Kings last week.
"Jason told us that his goal was to earn another contract with an NBA team. Today, I want to commend him on achieving his goal. I know everyone in the NBA family is excited for him and proud that our league fosters an inclusive and respectful environment," NBA commissioner Adam Silver said in a statement.
ESPN.com reported that the Nets quietly auditioned Collins last week in Los Angeles, paving the way from him to rejoin the franchise with which he spent his first six-plus seasons in the league.
The Nets were in the running to land Glen Davis but Davis opted to sign with the Los Angeles Clippers and informed teams of his decision. Davis is set to officially become an unrestricted free agent Sunday at 5 p.m. ET if, as expected, he is not claimed off waivers by another team.
Collins hasn't played in an NBA game since April 2013 with the Washington Wizards. Collins, who has a house in the Los Angeles area, said it was "pretty easy" to get to downtown for the game. He's been working out on his own for months in the L.A. area after failing to earn an invite to training camp from any of the league's 30 teams in the wake of revealing his sexual orientation to Sports Illustrated in April of last year.