The 29-year-old was a father-son recruit in 2010 and played 162 games for the Bulldogs, but cruelly missed out on the drought-breaking 2016 premiership through injury.
He played the first 17 games that year before breaking his leg.
Wallis began his career as a tagger, developed into a fully fledged midfielder and then transformed into a forward, leading the Bulldogs' goal-kicking in 2020.
But the valued leader managed just 11 games over the last two seasons as injuries took their toll.
Wallis underwent foot surgery in July and missed the remainder of the 2022 campaign.
"I've just got so much gratitude towards the Western Bulldogs Football Club," Wallis said.
"Playing for the red, white and blue was a childhood dream and this club has been my second home for more than a decade.
"Despite the disappointment of finishing at the Bulldogs, I will weigh up what comes next for me over the coming weeks.
"I wouldn't be the person I am today without the support of many people at the Bulldogs and their guidance, particularly over the past 12 months, and it's something I will always cherish."
Bulldogs coach Luke Beveridge, a Footscray teammate of Wallis' father Steve during the mid-1990s, paid tribute to the departing veteran.
"Mitch has been a highly respected and professional Bulldogs person from the day he arrived," Beveridge said.Â
"He has poured his heart and soul into his football.
"He has been a committed and supportive club man and an influential leader, having experienced the honour of being vice-captain.
"Unfortunately, he has been held back with injury at times, which has hindered his continuity and ability to influence on the field."
Wallis follows fellow father-son products Zaine Cordy (to St Kilda) and Lachie Hunter (Melbourne) out of the door at Whitten Oval this month, with Tom Liberatore, Sam Darcy and Rhylee West still on the list.
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