Lonie claimed best and fairest honours in a premiership campaign with Haileybury last year - his first season out of the AFL system since 2014.
The 26-year-old was drafted to St Kilda with the 41st overall selection of the 2014 National Draft and would play 87 games in the red, white and black for a return of 73 goals.
After being delisted at the end of last season, Lonie stepped back into local football, and will continue to play at the grassroots level with Seaford next season.
"The Seaford Football Netball Club are extremely excited to announce the signing of Jack Lonie," a club post to social media reads.
"After 7 years in the AFL playing for St Kilda, Jack most recently won a premiership and best & fairest at Haileybury in the VAFA.
"A Seaford Junior Football Club player, Jack played 3 games for the club in 2013 before embarking on his AFL career.
"Join us in welcoming Jack & his partner Ellie home to Seaford."
Seaford finished eighth in Division 2 of MPNFL in 2022, amassing eight wins and 10 losses.