Last season, Paajarvi played in 48 games for the Blues, scoring three goals and six assists (9 points). He also made three appearances in the Stanley Cup Playoffs, scoring one assist.
Paajarvi became a restricted free agent on July 1.
The 25-year-old Norrkoping, Sweden native has played in 276 career NHL games, scoring 35 goals and 45 assists (80 points).