The 6-2, 316-pound Grissom joins the Dolphins after spending time with the Kansas City Chiefs where he spent a portion of the 2014 off-season prior to being released on May 20, 2014. Grissom originally entered the NFL as an undrafted free agent with the New England Patriots following the 2013 NFL Draft. He spent the 2013 season on the Patriots reserve/injured after being placed on the list on August 1, 2013. Grissom was released by the Patriots on March 10, 2014. He signed with the Kansas City Chiefs on March 25, 2013. Grissom appeared in 46 career games, with 40 starts, at South Florida where he posted 105 tackles, 16½ tackles for loss, five sacks, three passes defensed, one forced fumble and one fumble recovery for the Bulls. He started the final 37 games of his career and was named second-team All-Big East as a senior. Born June 9, 1990 in LaGrange, Georgia, Grissom attended Troup County High School in LaGrange, Georgia.