Brady Tkachuk had a goal and an assist, and Claude Giroux scored for the Senators (8-10-0), who have lost three straight. Joonas Korpisalo made 19 saves.
Columbus went 2-for-2 on the power play, and Ottawa went 1-for-5 with the man advantage despite 16 shots.
“I felt we had the puck the majority of the game,” Senators coach D.J. Smith said. “Obviously, our penalty kill gave up two shots, two goals. I don’t think they had a lot of chances.
“We did enough things to win the game today. At the end of the day, we don’t get a couple of blocks and they get some tips, and they go into the net. We’ve got to find ways to score.”
Giroux gave Ottawa a 1-0 lead at 8:43 of the first period, taking advantage of a giveaway for a 2-on-1 before Tkachuk found him skating down the slot for the goal.
Tkachuk made it 2-0 at 11:08, scoring eight seconds into the power play on a one-timer from the right circle.
Patrik Laine cut it to 2-1 at 14:53 with a power-play goal from the top of the right circle.
“I honestly believe we deserved better,” said Senators defenseman Thomas Chabot, who returned after missing 10 games with a broken hand. “It was one of those nights. We had a great start, then they get a goal that bounces off someone like that. It’s part of the game, you can’t make excuses, but I thought if we play like that every night, we’re going to get better results more than not.”