The 21-year-old had been linked to Whitten Oval as soon as he parted ways with Geelong, and he joins the Dogs on second day of the delisted free agent window.
Hamling, who stands 194cm, failed to play a senior game in three seasons at Simonds Stadium.
"Getting in another key defender was important for us, and Joel adds a different dynamic to that group with his raw athleticism," Bulldogs list manager Jason McCartney said.
"Joel has been part of an elite development program at Geelong, and having watched closely throughout the year, we believe he is not far away from playing good consistent AFL football."
Hamling, who finished third in the Geelong's VFL best and fairest, is also capable of playing up forward, having booted five goals on one occasion this year.
The Bulldogs had interest in the Broome product in his draft year, but the Cats snapped him up with pick 32 in the 2011 NAB AFL Draft.
He is the second key defender the Bulldogs have secured in the past month after they recruited the highly rated Zaine Cordy through the father-son bidding system.
With five picks inside the top 50 at November 27's national draft, the Dogs may have to make a further delisting as they now only have four spots available on their list.
Injury-prone running defender Daniel Pearce or mature-age recruit Matthew Fuller loom as players who could make if way if the Dogs decide they want to use all five picks.
Clubs have until 2pm on November 13 to finalise their lists ahead of the draft.