The 20-year-old played just one senior match for the Dockers in 2013 to add to his five previous appearances over three seasons at Fremantle.
Mellington played in a WAFL premiership with West Perth in September, kicking 34 goals in 20 games with the Falcons including two in the WAFL Grand Final.
The Victorian recruit then requested a trade back home during the Gillette Trade period to be closer to his family and to gain further opportunities at AFL level.
But a trade was unable to be worked out and Mellington will now seek to find a new club during the delisted free agent period or the subsequent draft.
Mellington is the sixth Docker to be delisted this year alongside Jesse Crichton, Peter Faulks, Alex Forster and rookies Alex Howson and Haiden Schloithe.
Viv Michie was traded to Melbourne for a fourth-round pick in this year's NAB AFL draft. Jayden Pitt retired from football for health reasons.
The Dockers have added Colin Sylvia to their list through free agency and traded pick 55 to acquire key forward Scott Gumbleton.
Matt Taberner has been upgraded off the rookie list after playing four senior games in 2013.
Meanwhile, St Kilda rookie Jackson Ferguson has been delisted after three seasons with the club.
A former NSW scholarship selection, the 21-year-old was elevated ahead of round 10 and made his debut against North Melbourne in his only senior game for the club.
A key defender who enjoyed some strong performances for VFL club Sandringham during his time on the Saints' list, he came late to football and battled knee problems in 2013.