"We are absolutely fired up about adding a coach with Glenn's level of talent, pedigree and experience to the Rebel family," Arroyo said in a statement Thursday.
"He has demonstrated his ability to guide offenses and help players reach their full potential in both college and the NFL. He will play an integral role in our offensive game strategy and quarterback development."
Thomas spent the past three seasons as Baylor's co-offensive coordinator and quarterbacks coach. He followed former Bears coach Matt Rhule to Waco after a two-year stint as an assistant at Temple.
Thomas previously spent seven seasons in the NFL, serving three years as the Atlanta Falcons' quarterbacks coach after a four-year stint as an offensive assistant. He also had stints with the Baltimore Ravens, Jacksonville Jaguars and Midwestern State.
Arroyo, formerly Oregon's offensive coordinator, was hired on Dec. 11 to replace Tony Sanchez, who was fired after five seasons.
UNLV went 4-8 last season.