The 'Love Song' singer will round out a panel of three celebrity judges that includes Ben Folds and Shawn Stockman. Bareilles expressed her enthusiasm at joining the a cappella singing competition series in a press release from NBC.
"I'm extremely excited to be joining the panel of judges for The Sing-Off this fall!" Bareilles said. "A cappella music is very near and dear to my heart, and I have been a huge fan of the show from the beginning. I love the opportunity to be a part of something that celebrates a genre of music that I just adore and believe in. I can't wait for it to start."
Meanwhile, Paul Telegdy, executive vice president of alternative programming at NBC and Universal Media Studios, insisted that Bareilles will make a great addition to the reality show.
"Sara will bring a sublime technical knowledge and huge appreciation for The Sing-Off - she's a fan and we're thrilled she's coming on board," Telegdy said.
Bareilles replaces Nicole Scherzinger, who will be seen as a judge on The X Factor USA in the fall.
Auditions for the third season of The Sing-Off began in May.
The Sing-Off premieres on September 19 at 8pm on NBC.