The national director of the federal NDP is set to become deputy chief of staff to Alberta Premier Rachel Notley in January.
Anne McGrath has told NDP Leader Tom Mulcair she will remain in her current position until the end of the year.
"It's an incredible opportunity to work with such a progressive, principled, provincial leader," McGrath said in an interview with The Canadian Press.
McGrath's job change means she will join forces again with Brian Topp, Notley's current chief of staff.
Topp ran for the leadership of the federal NDP in 2012, but finished second to Mulcair.
Topp and McGrath were also members of the late Jack Layton's inner circle.
McGrath says she is looking forward to working with Notley, whom she has known for two decades.
"I think she is actually doing remarkable work and I think she is a leader in the country," McGrath said. "For instance, the recent announcements around Alberta's plan with respect to climate change and the whole way the new government, cabinet and caucus, have been developing over the last several months."
In a statement, Mulcair said McGrath has been a "tremendously talented" member of the NDP and wished her well in her new position.
"We will miss her terribly in Ottawa but she is moving back to her home province," Mulcair said. "I look forward to working with her in the Alberta government."
The federal NDP convention will be held in Edmonton in April, where Mulcair will also find out if he has enough support from rank and file party members to stay on as leader.