Mulvaney told the media that an advance team of scouts had started with about a list of possible locations for the summit in about a dozen states, and visited venues in California, Colorado, Hawaii, Florida, North Carolina, Michigan, Tennessee and Utah, the BBC reported.
"And it became apparent at the end of that process that Doral was by far and away, far and away, the best physical facility for this meeting.
"In fact I was talking to one of the advance teams when they came back and I said, 'what was it like?' And they said, 'You're not going to believe this but it's almost like they built this facility to host type of event.'"
Trump had originally floated the idea of his 800-acre Doral property hosting G7 earlier this year.
Denying that Trump would profit from the decision, Mulvaney said he had initially been sceptical and "aware of the political sort of criticism that we'd come under for doing it at Doral".
"I get the criticisms, so does he. Basically, he'd be criticised regardless of what he'd chose to do, but no there's no issue here on him profiting from this any way, shape or form."
The chief of staff also denied hosting the summit would breach the Emoluments Clause of the US Constitution, which prohibits a President from any "profit, gain, or advantage" received "directly or indirectly" from foreign governments.