Brown earned consensus All-America honors after leading the Longhorns with 15 tackles for loss and 6.5 sacks. He informed Texas coach Charlie Strong of his decision on Wednesday.
"Malcom had an unbelievable season and was a lot of fun to coach," Strong said in a statement. "He's a tremendous football player and a great young man who has a really bright future ahead of him. I know the decision was a difficult one, but we had some really good talks. He has our support and we wish him the best as he prepares for the NFL."
Brown is the No. 4-rated defensive tackle prospect, according to ESPN's Mel Kiper Jr.
He is No. 24 in the Scouts Inc. rankings, and was projected to go No. 22 to Pittsburgh in ESPN's Todd McShay's first mock draft.
The decision to go pro was an expected one throughout Brown's breakout season. The 6-foot-2, 320-pound lineman is married with two children and hopes to be drafted in the first two rounds to support his family.
"Coach [Chris] Rumph talked to me right after the [AdvoCare V100 Texas Bowl], and I talked to my wife about it," Brown said in a statement. "Then I went and saw Coach Strong yesterday, and we had a good talk about it. I decided to enter the 2015 draft, and that's what everyone thinks is best.
"It wasn't an easy decision because a lot went into it. My wife has school, I have school, and moving the kids around. I got everyone's input on it, but at the end of the day, it's my decision and that's what I came to."
The ESPN.com Big 12 Defensive Player of the Year started 26 games and recorded 165 tackles and 28.5 tackles for loss in three seasons at Texas.
"I'm always going to come back here," Brown said. "This is a great place with good people. I'm leaving good friends behind and created good bonds with people over the time I've been here. I'm always going to bleed orange, and I'm always going to support this program."