The deal announced Thursday was Pittsburgh's second in four days as the team attempts to shore up a banged-up lineup that's minus 12 regulars.
The 38-year-old Kovalev is a 17-year NHL veteran, who played for the Penguins from 1998 through the 2002-03 season before being traded to Montreal.
In exchange, the Penguins gave up a seventh-round pick in this year's draft. It will turn into a sixth-round pick if Pittsburgh reaches the second round of the playoffs and Kovalev appears in at least 50 percent of the first-round games.
Kovalev has 14 goals and 13 assists in 54 games this season.