Cook was selected in the third round (89th overall) by the Tennessee Titans in the 2009 NFL Draft. On July 7, 2009, he signed a contract with the Titans. In his rookie season, Cook finished the season with 9 receptions for 74 yards in 14 games.
Cook's second season was much more productive, he appeared in all 16 games including one start. He finished the season with 29 catches for 361 yards and one touchdown against the Kansas City Chiefs.
St. Louis Rams
Cook during 2013 Rams training camp.
Cook signed a five-year contract with the St. Louis Rams on March 12, 2013. after the Titans decided not to put the franchise tag on him following his request to be tagged as a wide receiver, which attracts a bigger pay.
|Ht Wt 40-yard||dash 10-yd||split 20-yd||split 20-ss 3-cone Vert||jump Broad BP|
|(112||kg) 4.50||s 1.60||s 2.64||s 4.56||s 7.25||s 41||in|
 In his first game with the Rams in 2013, Cook recorded 141 yards and 2 touchdowns on 7 receptions in a 27-24 win over the Arizona Cardinals.
He fumbled a possible third touchdown in the first quarter that was stripped by Tyrann Mathieu. His production slowed for the remainder of the season, but he still finished with 51 receptions for 671 yards and 5 touchdowns. He finished with almost identical numbers in 2014. Cook's tallies fell in 2015 to 39 catches on 75 targets for 481 yards.
He was released by the Rams on February 19, 2016.