Dumont, who has excelled in the A-League for more than a decade and has three Matildas caps, has signed with the Hawks as an "other sport rookie" for their upcoming campaign before returning to Victory next season.
She follows the likes of Brianna Davey, Jenna McCormick and Sarah Rowe in playing in the top-tier women's soccer and Australian rules football competitions.
Dumont is the reigning ALW goalkeeper of the year, was player of the match in last season's grand final win and went viral for her role in this season's elimination penalty shootout against Melbourne City, when she scored the opening spot-kick then saved the next.
The 31-year-old is a newcomer to the game but the Hawks were confident she could slot in and play a role.
"She may be new to Aussie Rules but her leadership, experience and knowledge of what it takes to succeed at the highest level will hold her in good stead as she embarks on a new journey in her career," Hawthorn AFLW list boss Mitchell Cashion said in a statement.
"To have a capped Matildas goalkeeper in our side will be extremely beneficial for our young playing group and we can't wait to see what Casey does in Hawks colours."
Dumont, who has won three ALW championships and two premierships, will also continue to work as a nurse while pursuing both sports.
Dumont who has previously been involved in World Cup, Olympics and Asian Cup squads, had been pressing her case for a Matildas recall.
But she appears at least fifth in line for Australia, with Mackenzie Arnold, Teagan Micah, Lydia Williams and Jada Whyman all called up ahead of her for recent friendlies against England and Scotland.
Victory said in a statement Dumont, who is contracted until the end of the 2023-24 season, had been "granted permission" to join Hawthorn over the off-season and ahead of their next campaign.
The AFLW season will commence on the first weekend of September with clubs to begin pre-season on May 29.
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