Jonathan Toews scored 42 seconds into overtime and assisted on Chicago's two other goals, as the Blackhawks rallied to beat Ottawa 3-2 on Tuesday night.
A pair of goals by Dominik Kubalik tied the score at 2-all early in the third after the Blackhawks trailed 2-0 early. Kubalik has seven goals this season.
Robin Lehner stopped 20 shots for Chicago, which was playing its first of a three games in eastern Canada.
Connor Brown and Chris Tierney scored first-period goals for the Senators. Rookie goaltender Marcus Hogberg started in net for the third straight game and made 27 saves.
Ottawa has just one regulation win in its last 14 games (3-5-6). The Senators are winless in their last eight (0-4-4).
Ottawa sped to an early lead. Brown scored 3:33 into the game, banging home a rebound of a shot by Dylan DeMelo.
Tierney gave the Senators a 2-0 lead less than four minutes later, scoring his seventh of the season by tipping in a pass from Thomas Chabot.
With time running out in the second, Kubalik cut the Senators' lead in half, deflecting a shot by Patrick Kane shot and beating Hogberg.
Kubalik then beat Ron Hainsey in a foot race 3:41 into the third and scored through Hogberg's pads for his 18th of the season.
The Blackhawks are at Montreal to take on the Canadiens on Wednesday.