The 28-year-old was one of five Hawks not offered a new deal by the club last month, ending his two-year stint at Waverley.
Hartley was first recruited into the AFL system by the Magpies ahead of the 2012 season, joining Collingwood as a Rookie selection.
The Penrith product was unable to break into Collingwood's senior side across his two seasons at the Holden Centre, with injuries riddling his time in the black and white.
Hartley was delisted by Collingwood at the end of the 2013 season, and eight years later, is set to return to the club's reserves structure.
According to The Leader, Hartley is set to link up with the Magpies for next season's VFL campaign, which promises to see out a premiership winner for the first time since 2019.
Due to the ongoing COVID-19 virus, the AFL has been forced to cancel the past two VFL seasons, with Richmond's 2019 Grand Final victory keeping the Tigers as the reigning premiers.
Richmond premiership coach Craig McRae has since been appointed as senior coach of Collingwood's AFL side following an impressive tenure at Punt Road and Hawthorn as an assistant.
While he won't directly oversee Hartley next season, the pair are set to reunite for the upcoming year.
Hartley played 49 games at AFL level, including 44 with Essendon after being recruited amid the club's infamous supplements saga.
With 12 players at Essendon banned for the scandal, Hartley was able to gain greater exposure at AFL level, playing 19 games in 2016 and a further 18 the following season.