With Faulk aging, Jackson was named the Rams' starting running back for the 2005 season. In Week 4, against the New York Giants, he had his first receiving touchdown on a 13-yard pass from Marc Bulger. In Week 7, against the New Orleans Saints, he had his first multi-touchdown game with two rushing in the 28-17 victory. In Week 8, against the Jacksonville Jaguars, he had 25 carries for 179 rushing yards to go with two receptions for 21 yards and receiving touchdown. Jackson had 1,046 rushing yards and eight rushing touchdowns on 254 attempts, and caught 43 passes for 320 yards and two receiving touchdowns.