Mark Jamar joins Essendon as a top-up player after being convinced by the Bombers to play in 2016.
The former Demon is understood to have made the difficult decision to resume his AFL career after much consideration.
"We obviously needed to add a ready-made ruckman to our list. Mark, as a big-bodied, All Australian ruckman will provide us with a great deal of experience," Essendon football manager Rob Kerr said.
"We feel Mark will work well with Matthew Leuenberger and assist with the development of our young players such as Gach Nyuon."