Sara Mearns was born in Columbia, South Carolina, and began her dance training at the age of three with Ann Brodie at the Calvert-Brodie School of Dance, also in Columbia. At the age of 13, Ms. Mearns trained with Patricia McBride at Dance Place, the School of North Carolina Dance Theatre, in Charlotte. She continued her studies at age 14 with Stanislav Issaev at the South Carolina Governor's School for the Arts and Humanities in Greenville. Ms. Mearns entered the School of American Ballet (SAB), the official school of New York City Ballet, full time in the fall of 2001. In the fall of 2003 Ms. Mearns became an apprentice with New York City Ballet. As an apprentice, Ms. Mearns danced a featured role in Michel Fokine's Chopiniana, performed by SAB as part of New York City Ballet's 2004 winter season. In June of 2004, Ms. Mearns joined the Company as a member of the corps de ballet. In March of 2006 she was promoted to soloist. In June 2008 Ms. Mearns was promoted to principal.

She performed in NYCB's Education Department lectures in January of 2003. Ms. Mearns also danced on a performance tour with North Carolina Dance Theatre in the winter of 1999.

Ms. Mearns is a 2003 recipient of the Mae L. Wien Award and a 2003 nominee for the Princess Grace Award.