The person spoke to The Associated Press on the condition of anonymity because the Penguins had not announced the deal, reached a half hour into the start of the NHL's free agency period on Tuesday.
Ehrhoff became a free agent on Sunday after the Buffalo Sabres bought out the final seven seasons of the player's 10-year contract.
He's a 10-year NHL veteran who spent the past three seasons with the Sabres. Overall, the German-born Ehrhoff has 69 goals and 313 points in 692 games.
The Penguins are restocking on defence with Matt Niskanen and Brooks Orpik both entering free agency.
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