The appearance of Cliburn, 78, at the Thursday event had been kept secret from most people in the audience, as well as in the symphony, the Fort Worth Star-Telegram reported.
"He is on oxygen and he is very frail," said Alann Sampson, the interim president and chief executive officer of the Van Cliburn Foundation. "But he was hoping to make the appearance, as much as possible."
Many audience members and musicians were moved to tears during Cliburn's speech.
"Van's been the spiritual center of classical music in Fort Worth for a very long time," said Paul Unger, assistant principal bass for the symphony. "It was really inspiring to be there. I think there was a tear in every musician's eye. It just made the whole evening extra special."
As he left the stage, Cliburn told the audience: "I'll love you all from the bottom of my heart forever."