Sanchez was signed to a four-year contract paying him $500,000 plus bonuses.
University officials announced the11-0 vote on Tuesday, days after Sanchez was named to the job by UNLV President Donald Snyder and athletic director Tina Kunzer-Murphy.
UNLV becomes one of a small number of Division I schools to hire a head coach directly from the high school ranks.
The 40-year-old Sanchez was 85-5 in six years at Bishop Gorman in Las Vegas, the top-ranked high school team in the country.
He replaces Bobby Hauck, who resigned in November after compiling a 15-49 record in five seasons at UNLV.
The Rebels were 2-11 overall this year and 1-7 in the Mountain West Conference.