Bennell was thrust into the media spotlight midway through 2015, after photos of him ingesting an illicit substance were splashed across The Herald Sun in Melbourne.
The 23-year-old was also involved in an incident at a Gold Coast nightclub, that saw the promising youngster arrested post-season, and brought to an end his controversial tenure with the expansion club.
The Dockers struck a deal with the Suns, who will receive picks 16 and 35 in this year’s national draft in exchange for Bennell and pick 22.
Bennell was taken at pick number two by the Suns in the 2010 National Draft, and signalled his intention to return to his home state of Western Australia following his time on the Gold Coast.
“I’m excited about returning home to WA and joining Fremantle,” Bennell said in a statement on the Dockers’ website.
“My main focus now is to knuckle down and have a solid pre-season over the coming months.”