On June 1, 2015, Walcott was traded from the New York Rangers to the Tampa Bay Lightning in exchange for a seventh round draft pick in the 2015 NHL Entry Draft, which was initially sent to Tampa Bay in the Martin St. Louis trade the previous season. Walcott had just finished his second season in Quebec Major Junior Hockey League with the Blainville-Boisbriand Armada. Walcott had seven goals and 41 points in 54 regular season games. He additionally appeared in one American Hockey League game with the Hartford Wolf Pack after signing an amateur tryout agreement.