In overtime, Schwartz took the puck behind the net in his own end and skated all the way down the ice before firing a wrist shot past Bruins goalie Anton Khudobin for his 22nd tally of the season.
It was the third straight game in which St. Louis fell behind and came back to win in overtime. The Blue now have 85 points and sit two points out of the final wild-card spot in the Western Conference.
"We've got that belief back in ourselves," Schwartz told NBC Sports Network after the win. "We went through some adversity a few weeks ago. It was tough on us, but I think learned from it and realized how tough it is to win, and I think it made us a lot more hungry."
St. Louis had dropped seven consecutive games and nine of 10 from Feb. 11 to March 8.
Ryan Donato scored the lone goal for Boston, which clinched a playoff berth for the second straight season under new coach Bruce Cassidy with a point, Boston's 100th. The Bruins have lost two straight and four of six (2-2-2).
Jake Allen recorded 21 saves in the winning effort for the Blues while Khudobin had 18 saves for the Bruins.
Boston jumped on top with 9:48 remaining in the first period. Alex Pietrangelo's clearing attempt from behind the St. Louis net deflected off a referee and trickled right to Donato, who slammed in a power-play goal.
Donato scored a goal and had two assists in his NHL debut Monday in a 5-4 overtime loss to Columbus. The 21-year-old former Harvard standout joined the Bruins last Sunday on a two-year, entry-level contract.
After a scoreless second, Schwartz tied the game with 10:24 left in the third. He received a feed from Alexander Steen at the top of the left circle and fired a wrister past Khudobin.
Dmitrij Jaskin's backhanded effort off a rebound in front of the net was stopped by Khudobin in the closing seconds to force overtime and send the Bruins into the playoffs.
--Field Level Media
Boston | St. Louis | |
Ryan Donato 1 | Points | Jaden Schwartz 2 |
Ryan Donato 1 | Goals | Jaden Schwartz 2 |
Ryan Donato 0 | Assists | Brayden Schenn 2 |
Ryan Donato 1 | Power Play Goals | N/A |
N/A | Short Handed Goals | N/A |
Anton Khudobin .900 | Save Percentage | Jake Allen .955 |
Anton Khudobin 18 | Saves | Jake Allen 21 |
Team | Shots | Goals | Power Play | Penalty Kill | Penalty Mins | Face Offs Won |
Boston | 22 | 1 | 1-2 | 2-2 | 6 | 20 |
St. Louis | 20 | 2 | 0-2 | 1-2 | 6 | 28 |