Gardner joined the Bulldogs via the 2019 Mid-Season Draft after being delisted by Geelong at the end of the season prior without featuring at AFL level across three years with the Cats.
The 24-year-old has since played 17 games in the blue, red and white under Luke Beveridge and has played five games in 2021 after battling a shoulder injury.
Speaking to the Bulldogs' website, Gardner stated his excitement to extend his stay at the Kennel.
“It’s great to have another couple of years. It’s been a really enjoyable time and a great bunch of boys, which is really helping me to strive to be better,” Gardner said.
“Confidence is the main thing for me. To be able to play those 10 games last year, I came into this season feeling a lot more confident in my ability. Putting another pre-season on the board down back with the team was really good as well.
“(Defensive coach) Rohan Smith has been really good for my development – helping me to get better in my position and understand everything I need to do out there.
“For me now it’s just making sure each week I’m consistent and keep striving to get better and better each week.”
Gardner has been a formidable role player down back for the Dogs this year, with Beveridge's side currently placed with the second best defensive record in the league.