Hunter, who was hired to replace Bruce Boudreau in November after the Capitals went on a 3-7-1 stretch, went 30-23-7 the rest of the way and helped Washington clinch a play-off berth in their penultimate game of the regular season.
"I thought he did a great job of coming in and helping us out," Capitals General Manager George McPhee said.
"Trying to hire a coach in the middle of the season is a difficult process. ... So to have Dale available to come in, even if on a temporary basis, was something we liked a lot."
Hunter, 51, will return to the London Knights of the Ontario Hockey League, where he coached for 11 seasons before taking the Capitals job last year, according to McPhee.
Under Hunter, the Capitals stunned the defending Stanley Cup champion Boston Bruins in the first round of the play-offs before falling to the top-seeded New York Rangers in a decisive seventh game of the Eastern Conference semi-final.