Julie Kent will replace Ferri in the title role of Giselle on July 11 and July 15.
The July 15 performance was also to serve as a celebration of Ferri's 20th anniversary with the company. Instead, the ABT will salute the dancer after the performance.
Born in Italy, Ferri studied at the ballet schools of La Scala and the Royal Ballet, and joined the Royal Ballet in 1980. She came to ABT as a principal dancer in 1985.