Matthew Tkachuk was the lone goal scorer, with Johnny Gaudreau getting one of the assists.
Earlier in the day, Gaudreau was named to the roster for the upcoming all-star game in Las Vegas (more on that below).
Tkachuk, meanwhile, will be one of the players vying for a spot in the game via the Last Men Inonline voting (also more on that below).
Jacob Markstrom got the start for the Flames and made 27 stops, while Matt Murray had 30 saves for the Sens.
It was Calgary's first game at the 'Dome since way back on Dec. 11 when they fell to the Bruins.
It was just the Flames 12th home game of the season, while they've skated 22 times on the road.
The Sens got on the board quick, tallying 1:43 in on their first shot of the contest when Nick Paul beat Markstrom with a fading wrister from the high slot.
The Flames got a couple cracks to tie it up.
Murray got a piece of Gaudreau's offering with his glove on a 2-on-1 with Elias Lindholm, then later it was Dillon Dube with an incredible behind-the-back pass to Brett Ritchie on the doorstep but he couldn't beat the Ottawa 'tender.
Ottawa hemmed Calgary in their own zone with four minutes left in the first and it led to their second goal of the night, Connor Brown driving low and passing to Paul, who went forehand/backhand at a full gallop to put the puck home as he cut across the zone at 16:37.
Early in the second period, Milan Lucic looked to get his side going with a fight against Scott Sabourin, the Flames big man winning the lengthy tilt in a decided fashion, landing a boatload of big bombs.
Tkachuk came close to tying it up when he got a couple whacks at a puck that was beside the left post but Murray blocked it.
Near the midway point of the frame, the Flames had some prolonged pressure and Gaudreau skated out from behind the net and feed Oliver Kylington as he snuck in from the point all alone but Murray squeezed into the right post to deny the shortside shot.
With 57 ticks left in the middle stanza, Drake Batherson increased the visitors' lead when his tough angle shot found a small hole over Markstrom's shoulder.
Tkachuk showed off his sweet hands by cutting through the slot and tipping a Chris Tanev shot past Murray at 47 seconds into the third period.
Eight of of his 16 goals have come on 'Dome ice this year.
