Hartley reportedly will be introduced at the noon EST news conference, a month after he was fired by the Colorado Avalanche.
A native of Hawkesbury, Ontario, he would replace general manager Don Waddell, who has been serving as interim coach since Curt Fraser was dismissed on Dec. 26.
Former Washington Capitals, Philadelphia Flyers and Florida Panthers coach Terry Murray also interviewed with Atlanta.
Hartley's hiring was reported Saturday. THe report said the Thrashers were waiting for Hartley to resolve financial issues with the Avalanche. He is expected to make his Atlanta debut on Wednesday against the Montreal Canadiens.
Hartley's firing came just 18 months after he guided the Avalanche to the Stanley Cup championship. The 42-year-old is the second-winningest coach in franchise history with a 193-109-48-9 record and won four division titles in four-plus seasons.
In their fourth season, the Thrashers are last in the NHL with an 11-25-2-4 record and 28 points. They are 2-5-1-0 under Waddell.
Until the 2002-03 campaign, the last coach to work for two teams in the same season was Ted Sator, who guided the New York Rangers and Buffalo Sabres in 1986-87. But Darryl Sutter was hired by the Calgary Flames on Dec. 28, four weeks after he was fired by the San Jose Sharks.