On March 7, 2015, the Jacksonville Jaguars re-signed Alualu to a two-year, $6 million contract. He participated in training camp and competed for the starting defensive end job with Chris Clemons, Jared Odrick, Ryan Davis, Andre Branch, and Chris Smith. He was named the starting defensive end with Chris Clemons to begin 2015.
In a Week 5 loss to the Tampa Bay Buccaneers, Alualu collected a season-high four combined tackles. On October 12, 2015, he recorded a tackle and sacked Tennessee Titans' quarterback Charlie Whitehurst during a 16-14 loss. During the 2015 season, he played all 16 games starting 14 of them, making 26 tackles (18 solo), two sacks, two passes defended, and a fumble recovery.