Radulov, 25, has been one of the top scorers of the Russian Kontinental Hockey League since he broke his Nashville contract to return home. He was named the KHL's most valuable player for the 2009-10 and 2010-11 seasons.
He is expected to provide a lift at right wing for the Predators in the post-season, General Manager David Poile said.
"Adding the best player in the world not currently in the National Hockey League can only help the Nashville Predators," he said. "Alex is a terrific talent and a proven goal-scorer who will now have a chance to help the Predators and play against the best teams and players in the world."
Poile said the Predators "always believed he would return."
Radulov posted 26 goals and 32 assists in 81 games during his best season for the Predators -- 2007-08.
The high-scoring will play the rest of this season under the terms of his original entry-level contract signed in 2006, and then will become a restricted free agent.