Terms of Hartley's new deal were not disclosed by the NHL franchise but the 54-year-old's current contract was set to expire at the end of the season.
The Flames (17-14-2) are struggling for form this season, fifth in the Western Conference Pacific division with 36 points having lost their past six games including Tuesday's 5-2 defeat at home to the New York Rangers.
Hartley is in his third season as coach of the Flames since replacing Brent Sutter in May 2012.
The former Colorado Avalanche boss boasts a 71-79-13 record with the Flames.