He faces up to 20 years in prison for a December 2012 wreck after a night of partying with fellow Cowboys players. He could also get probation.
Jurors took about nine hours over two days to convict Brent, who was led from the courtroom in handcuffs as family members sitting in the front row of the gallery sobbed.
Among those sitting with Brent's family was Stacey Jackson, Brown's mother. Jackson did not respond to questions as she left the courtroom Wednesday with Brent's family, but she has said in interviews that she's forgiven Brent and could testify in support of a lighter sentence for him when that phase of the trial begins Thursday.
Attorneys from both sides remain under a gag order that prevented them from commenting after the proceedings.
"We understand the very serious nature of this situation and express our concerns for all of the families and individuals that have been affected by the tragedy of Jerry Brown's death," Cowboys owner Jerry Jones said in a statement.
Prosecutors say Brent, a defensive tackle, was drunk when he crashed his Mercedes on a suburban Dallas highway in December 2012, killing Brown, a linebacker on the Cowboys practice squad who had also been Brent's teammate at the University of Illinois. Officers who arrived on scene saw Brent trying to pull Brown's body from the wreckage.
Police say Brent's blood alcohol level was tested shortly after the crash at 0.18 percent, more than twice the legal limit for drivers in Texas. Prosecutors last week argued that the burly, 320-pound defensive tackle had as many as 17 drinks the night of the crash.
Brent's attorneys argued the blood tests used by police were faulty and that Brent couldn't have had nearly that much to drink. Attorney George Milner said his client was "guilty of being stupid behind the wheel of a car," not drinking beforehand.
Brent retired from the NFL last year, but his ties to the Cowboys were prominent at trial. Two current players, Barry Church and Danny McCray, testified about hanging out with Brent and Brown, first playing video games, then having dinner and going to Privae, a Dallas nightclub.
Sean Lee, a Cowboys linebacker, attended part of the trial to show support for Brent, and Jones said this week that he was closely watching for a verdict.
"Certainly it's tragic. We've all, to some degree, have been a part of this," Jones said on Tuesday, according to the Cowboys' website. "We support Josh. This has been just a terrible experience for the families who lost a loved one and for Josh who loved Jerry as well."
Jurors saw video of Brent appearing to hold bottles of champagne in each hand and credit-card receipts that showed Brent had purchased three bottles. They also saw police dash cam footage of Brent losing his balance during field sobriety tests and occasionally stumbling over his words while talking to officers.
It was, in the words of prosecutors Jason Hermus and Heath Harris, a textbook case of intoxication manslaughter. The prosecutors told jurors in their closing argument that they should send a message about the danger posed by drunken drivers.
Hermus stood in front of Brent, hit the table and shouted: "They shouldn't be driving, no exceptions, no excuses!"
Prosecutors have indicated they will push for jail time for Brent. His conviction comes just after weeks of fierce debate about a North Texas teen, Ethan Couch, who received probation for intoxication manslaughter after a wreck that left four people dead. Couch's case, and the so-called "affluenza" defense his attorneys employed, became the subject of fierce, widespread scrutiny.
Dallas County District Attorney Craig Watkins has attended parts of Brent's trial and whispered in prosecutors' ears during the questioning of one witness. Watkins told a sports radio station last year that prosecutors had the responsibility to make sure Brent "loses his freedom."
Brent, a defensive tackle, had played in all 12 games of the 2012 NFL season before the crash. He retired in July.
Brown was signed to the Cowboys' practice squad in the 2012 season.
Information from The Associated Press was used in this report.