Sebastián Villarini-Vélez was born in San Juan, Puerto Rico. He trained with Rodney Rivera, Joaquin Banegas, and Maria Carrera, and also studied dance at the School for the Performing Arts in Puerto Rico with teachers including Yolanda Muñoz and Jose Rodriguez. In 2007, he attended the Miami City Ballet School summer course under the direction of New York City Ballet (NYCB) alumnus Edward Villella in Miami, Florida and later the Pacific Northwest Ballet School summer program in 2011 under the direction of NYCB alumnus Peter Boal in Seattle, Washington.
Mr. Villarini-Vélez began studying at the School of American Ballet (SAB), the official school of New York City Ballet, during the 2008 summer course, which he attended again during the summer of 2010 before enrolling as a student that fall.
In August 2012, Mr. Villarini-Vélez became an apprentice with NYCB and joined the Company as a member of the corps de ballet in August 2013.
He was promoted to soloist in October 2018.