The Lions made the announcement on Thursday evening in what is yet another injection of star power into the competition.
Lynch, a former Western Bulldogs utility, has nominated Seymour as his home club while he continues his VFL career with Essendon.
The dashing speedster, who played nine games at the elite level across four seasons, joins the likes of former AFL talent Michael Hartley at the Lions.
Seymour coach Ben Davey said Lynch’s connection with Seymour product Josh Schache opened the door for him to land at Kings Park.
“We’re very happy to have him. He’ll be a terrific addition to the side when he’s available,” Davey said.
“Brad is really good mates with Josh from his time at the Bulldogs and he then met and became mates with a few of the Seymour boys that grew up with Josh.
“He’s on Essendon’s VFL list and he needed a home club ... we were lucky enough he signed with us. Hopefully Brad can play some good footy at VFL level and then get looked at in the mid-season draft, so we’re expecting him to only be available in Essendon’s bye rounds.”
Originally drafted by the Bulldogs with pick 11 in the 2016 rookie draft, Lynch showcased his skills across half-back in an injury-plagued career.
Following his exit from the Bulldogs in 2020, the 25-year-old has since developed his game in Queensland where he played for state-league outfit Southport and then Broadbeach in 2022.
“He’s a quality player who has great speed, he’s a good user of the ball and he kicked over 40 goals last year,” Davey said.
“He can play at pretty much either end of the ground.”