The 18-year-old newcomer will star in Luhrmann's 1970s-set Netflix drama, which follows the rising popularity of hip-hop, punk and disco, reported Variety.
Guardiola will play Mylene Cruz, a singer from a religious background who dreams of becoming a disco star.
The actress joins previously announced cast members Shameik Moore, TJ Brown, Justice Smith and Skylan Brooks.
Luhrmann's music drama follows a "rag-tag crew" of South Bronx teenagers who come to change the music scene of the '70s.
"The Get Down" will consist of 13 60-minute episodes which will air on Netflix in 2016.