Agnes Su was born in Newport Beach, California, USA and grew up in San Clemente and Irvine, California. She received her first ballet lessons at the Pacific Coast Academy of Dance in San Clemente before she went to the Southland Ballet Academy. In 2010 she came to the John Cranko Schule in Stuttgart where she graduated in 2013. During her last year at the Academy of the John Cranko Schule she already danced in several productions of the Stuttgart Ballet in the Corps de ballet.
In the years 2008 to 2011 she took part in the Youth American Grand Prix. In 2009 she won the Hope Award at the Regionals in Huntington, in 2011 the Junior Grand Prix at the regionals in San Diego.
In the season 2013/14 Agnes Su became an apprentice with the Stuttgart Ballet, one season later she was taken into the Corps de ballet. In January 2017 she was promoted to Demi Soloist, in the 2019/20 season to Soloist.