In the 2013 season, Decker contributed to Peyton Manning's historical passing season. In Week 3, against the Oakland Raiders, Decker finished with eight receptions for 133 yards and a touchdown. In Week 7, against the Indianapolis Colts, he finished with eight receptions for 150 yards and a touchdown. In Week 13, Decker had a career day against the Kansas City Chiefs with eight catches for 174 yards and team record tying four touchdowns, earning him the AFC Offensive Player of the Week award. He followed up that performance with eight receptions for 117 yards and a touchdown against the Tennessee Titans. In Week 16, against the Houston Texans, he finished with 10 receptions for 131 yards and two touchdowns. Overall, Decker finished the 2013 season with 87 receptions for 1,288 yards, both career highs, and 11 touchdowns. The Broncos reached Super Bowl XLVIII, but lost 43–8 to the Seattle Seahawks. Decker was held to one reception for six yards in the Super Bowl due to tight coverage by the Seahawks' defensive backs.