The Silicon Valley entrepreneur and SurveyMonkey chief executive Dave Goldberg died of severe head trauma, according to local officials.
Mr Goldberg, 47, husband of Facebook executive Sheryl Sandberg, was found lying next to a gym treadmill on Friday at a holiday resort in Mexico.
Mexican authorities have no plans for a criminal investigation.
The officials said Goldberg still had vital signs when he was discovered, but later died at a hospital.
He reportedly left his room in the resort near Nuevo Vallarta at 16:00 local time to exercise, and family members went to look for him when he failed to return.
He was found at about 18:30 in the gym, lying by a treadmill, with a blow to the lower back of his head.
It was apparent he had slipped on the treadmill and hit the machine, a spokesman for the Nayarit state prosecutor said.
A Harvard University graduate, Mr Goldberg joined SurveyMonkey in April 2009. Before that, he was a entrepreneur, venture capitalist, and technology and music industry executive.
He founded one of the first online music services, Launch Media, in 1994 and led the company until its acquisition by Yahoo in 2001.
Following the sale, Mr Goldberg became vice-president and general manager of Yahoo Music, where he led the company's global music operations.
From 2007 until he joined SurveyMonkey in 2009, he served with venture capitalists Benchmark Capital.