 On 31 July 2015, Morison was given the number 20 shirt for the upcoming 2015/16 season.On 4 August 2015, Morison rejoined League One club Millwall for a third spell, for an undisclosed fee.Morison moved into the top ten of Millwall's all-time top scorers, after scoring six goals in eight games to begin the 2016–17 season.