The scrum-half, who has won 16 caps, will move to the Liberty Stadium from Ospreys' fellow RaboDirect PRO12 team Zebre.
And he is set to fill the void left by Samoa scrum-half Kahn Fotuali'l, who is set to join Aviva Premiership club Northampton next term.
Tebaldi, 25, said: "I am excited about this fantastic opportunity with the Ospreys.
"Their record in the PRO12 speaks for itself, and the chance to be a part of such a successful club is something I couldn't turn down.
"I am looking forward to a new challenge in a competitive environment that will help me to improve as a player and a person, while hopefully contributing to the continued success of the Ospreys."