Mike Comrie scored twice, Daniel Alfredsson and Peter Schaefer each added a goal and an assist, and the Senators handed the Washington Capitals' goaltender his first defeat against Ottawa with a 5-2 victory before a crowd of 18,810 at Scotiabank Place.
Johnson came into the game 3-0 for his career against the Senators (27-19-2), but Comrie, who missed practice a day earlier because of an undisclosed injury, returned and contributed a first-period power-play goal and added another in the second as Ottawa won its fifth straight contest.
"We played a very smart game. We capitalized on our opportunities when we had to, and we're being rewarded for our hard work," said Comrie, who ran his goal total to four in seven games with the Senators since being acquired in a trade from Phoenix on Jan. 3.
Andrej Meszaros had the other goal for the red-hot Senators, who have now won six of their past seven contests.
Alfredsson's shorthanded goal early in the second period stood up as the game-winner - the fourth straight time he's had that distinction.
"It's more luck," said Alfredsson, who, with the two points, has 14 during his current five-game point streak. "It's nice to score goals and it's nice to keep winning.
"We scored some timely goals."
Ottawa improved to 10-1-1 in its last 12 games and moved past the Montreal Canadiens, who were beaten 4-0 by the Vancouver Canucks last night, into second place in the Northeast Division and fourth in the Eastern Conference overall standings.
"It's nice to keep jumping up," said Alfredsson about the standings. "It can change quickly again, but we've just got to win our games and give ourselves a chance to win every
Ray Emery stopped 28 shots to earn his 20th victory of the season in the Senators' net, while Tom Preissing chipped in with a pair of assists.
Steve Eminger, with his first of the season, had a goal and an assist for Washington (19-20-7), which suffered its third straight loss.
Chris Clark had the Capitals' other marker while shorthanded and Johnson finished with 29 saves.
The Capitals tried to ride Johnson's luck against the Senators and handed the goaltender his first start in 10 games, since Dec. 26, in place of Olie Kolzig.
He had a 0.92 goals-against average and .972 save percentage in his three previous wins against the Senators, including a 46-save performance in a 1-0 triumph in Washington's last visit to Ottawa on April 1, 2006.
However, the Capitals struggled to generate chances against the Senators and Ottawa improved to 10-3-1-1 against Washington since the 2002-03 season.
"We're not trying to do too much, we're trying to work hard as a collective group. When you do that, you win games," Comrie said.
The Capitals have just four wins in the past 14 games.
"We need a victory any way they come - gritty goals, goals in front of the net - we need a bounce here or there," Johnson said. "There's nothing anyone can say, it's just up to ourselves to do it."
Johnson had to make a couple of good saves early, including a pad stop on a deflected shot by Daniel Alfredsson.
With less than four minutes remaining in the period, he couldn't stop Meszaros' drive from the point, however, and the Senators took a 1-0 lead.
Comrie doubled the advantage on the power play with 30 seconds to go in the period and the Capitals appeared to be in trouble when defenceman Brian Pothier, an ex-Senator, compounded their troubles by taking another minor penalty, but Clark brought Washington back into the game with a shorthanded goal with 2.3 seconds left in the period.
Alfredsson jumped on a loose puck at the side of the Capitals' net to score his own shorthanded goal and restored Ottawa's two-goal cushion midway through the second and, 67 seconds after that, Comrie scored his second of the game from the slot after a feed from Peter Schaefer.
Ovechkin showed some frustration in third period. After breaking his stick while on the attack in the Senators' zone, he tossed his broken shaft to the ground and ran over Ottawa's Dany Heatley from behind on his way to the bench.
No penalty was called on the play and it gave the Capitals a slight boost. Eminger scored shortly afterward to make it 4-2. Ovechkin drew an assist on the play to extend his point streak to seven games.
Schaefer closed out the scoring with 6½ minutes remaining, flipping the puck past Washington defenceman Jamie Heward and slapping it past Johnson.
"They keyed in our top line tonight," Johnson said. "They shut (Dainius) Zubrus, Ovechkin and (Alexander) Semin down.
"I was very confident at the start of the game. If we'd just got different bounces here or there, it could have been a different game."
Notes: The Senators were still without centre Jason Spezza and Mike Fisher because of knee injuries. Spezza, who returned to practice Monday, has missed the last 12 games while Fisher has missed the past 10. ... Centre Kris Beech was a healthy scratch for the Capitals. ... Washington plays at Carolina on Thursday, returns home to face Florida on Saturday, then plays the Hurricanes in back-to-back games Jan. 26 and 27.