Djou won the special mail-in election with 39.7 percent of the vote in the final printout, released at 9 p.m.
The final printout represented 171,417 ballots returned by voters in the district, which stretches from Waikiki and downtown to Mililani.
Democrat Colleen Hanabusa was second at 31 percent, with Democrat Ed Case third at 27.8 percent.
“This is a momentous day,” Djou told a jubilant crowd at state party headquarters. “We have sent a message to the United States Congress. We have sent a message to the ex-governors. We have sent a message to the national Democrats! We have sent a message to the machine.
“We have told them that we will not stand idly by as our great nation is overburdened by too much taxes, too much debt and too much wasteful spending.”
November's election will be more difficult to win for Djou because Hawaii is a liberal state and he will be only facing one challenger, so the Democratic vote will not be split, but it is doable for Djou if he continues to get his message out there.
The optics of a Republican winning the seat after 20 years of Democrats holding it, in Obama's "home" are not good for the Democratic party.