The deal is worth $19.25 million, carrying a $3.85 million cap hit.
Berglund was set to become a free agent on July 1, and was among possible trade targets for teams needing a rental forward ahead of the NHL Trade Deadline.
Berglund, 28, has spent his entire career with the Blues since being drafted in the first round (25th overall) by the club in 2006.
The Swedish centreman has tallied 145 goals and 141 assists in 615 career regular season NHL games, adding 10 goals and a dozen assists in 49 playoff contests.
February 24, 2017