Franco was born in the city of Yuma in southwestern Arizona to Mexican parents. He has described his upbringing as working class.
Franco first started acting in a number of television comedies. His first major credit was as Spencer Diaz in the first season of the 2017 Netflix comedy American Vandal. In 2019, he had a supporting role in the critically acclaimed comedy film Booksmart. He also appeared in several nationwide commercials, including spots for GEICO, Samsung, and TurboTax. In 2020, Franco starred in a lead role as Andrew in the Hulu movie The Binge.
In 2022, Franco gained notability for playing Argyle, a stoner friend of Jonathan Byers, in the fourth season of Stranger Things. Franco initially auditioned for the role of Eddie Munson.