The 6-3, 283-pound Allen, who led the Crimson Tide with 12 sacks and 14.5 tackles for loss, announced his decision Saturday on Twitter and confirmed to university officials that he's returning.
Allen, who has 18 sacks in his three seasons with the Crimson Tide, had met with Alabama coach Nick Saban about his draft status earlier this week and didn't join teammates Derrick Henry and A'Shawn Robinson on Friday as they announced their intentions to turn pro.
ESPN's Mel Kiper Jr. projected Allen, had he decided to enter the draft, to go to the Buffalo Bills with the 19th overall selection in his Mock Draft 1.0. Kiper also rated Allen as the fifth-best defensive end prospect on his board in December.
The deadline for nonseniors to declare is Monday.