The deal is worth $4 million, the team said.
Ehrhoff was expected to garner significant interest on the open market since being bought out of the remaining seven years of his 10-year, $40 million deal by the Buffalo Sabres, so it was surprising when the 31-year-old German-born blue-liner opted for such a short-term deal.
Penguins general manager Jim Rutherford adds a defenseman at a reasonable price as Ehrhoff had the flexibility of finding a spot that fit his immediate needs.
Ehrhoff had six goals and 33 points in 79 games last season for the Sabres.
The Penguins also re-signed Nick Drazenovic to a one-year deal for $550,000. The 27-year-old forward had 13 goals and 29 assists at Wilkes-Barre/Scranton of the AHL.