The Predators, who made it to the Stanley Cup finals last year, locked up the Presidents' Trophy (top point total in the league) later Thursday when the Boston Bruins lost to the Florida Panthers.
Nashville earned its 52nd victory of the season, a franchise record.
The game-winning play began when Viktor Arvidsson fired a shot from the left wing that Washington goalie Philipp Grubauer got a glove on. However, the puck then squirted loose in the crease, and Johansen tapped it into the net.
Craig Smith led Nashville with two goals. Johansen finished with one goal and one assist, as did teammate Roman Josi.
Ryan Ellis and Kyle Turris both had two assists for Nashville in the victory.
Washington already has clinched the Metropolitan Division title, which it locked up earlier this week with a victory over Pittsburgh.
Evgeny Kuznetsov led the Capitals with two goals and one assist.
The first three goals of this game all came on the power play. Smith gave the Predators a 1-0 lead by scoring on a rebound from right in front 4:17 into the game.
Washington tied the game at 4:29 of the second period when Alex Ovechkin scored an extra-man goal on a bullet from the left side. The Capitals then took a 2-1 lead when Kuznetsov scored at 6:47 of the period.
Kuznetsov was trying to make a pass across the crease but the puck hit a Nashville player and then slid into the net.
Smith then tied the game with 5:57 left in the period, scoring on a rebound from in front after a shot bounced off goalie Grubauer's chest.
Kuznetsov's second goal gave Washington a 3-2 lead 1:07 into the third period. He came in along the right wing and put a backhand shot past goalie Juuse Saros on the short side.
Nashville tied it 8:19 into the third period on a Josi power-play goal.
The Capitals held a pre-game ceremony honoring Ovechkin for being the first Capital in franchise history to play in 1,000 games.
--Field Level Media
Nashville | Washington | |
Craig Smith 2 | Points | Evgeny Kuznetsov 3 |
Craig Smith 2 | Goals | Evgeny Kuznetsov 2 |
Ryan Ellis 2 | Assists | Evgeny Kuznetsov 1 |
Craig Smith 1 | Power Play Goals | Evgeny Kuznetsov 1 |
N/A | Short Handed Goals | N/A |
Juuse Saros .906 | Save Percentage | Philipp Grubauer .862 |
Juuse Saros 29 | Saves | Philipp Grubauer 25 |
Team | Shots | Goals | Power Play | Penalty Kill | Penalty Mins | Face Offs Won |
Nashville | 29 | 4 | 2-2 | 3-5 | 10 | 36 |
Washington | 32 | 3 | 2-5 | 0-2 | 4 | 29 |