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 face-off 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.”