Since his move from the Cornish Pirates in 2006, Bearman has become a supporter's favourite in Newport and made 72 appearances for the Welsh region.
"I am really looking forward to linking up with the Ospreys," said Bearman.
"This is an excellent opportunity for me to play top level rugby that I could not turn down.
"I have enjoyed five good years at the Dragons but I felt the time was right for a new challenge and a change of environment. There were four or five really good offers on the table but it was the Ospreys who really impressed me.
"The management at the Ospreys have a plan for what they want to achieve and I really like what I have seen of the young talent playing for them over the last couple of months.
"I have got a bit of experience which I can bring to this young squad, I have played a bit of rugby and I hope to give something extra to the group."
Ospreys elite performance director Andrew Hore expressed his delighted at the signing.
"Joe comes to us with an excellent reputation for being an honest, hard working individual who thrives on the physical side of the game and is particularly renowned for his ability to make the hard yards with the ball in hand," he said.
"With his experience I have no doubt he will prove to be a huge asset to the Ospreys on and off the field."