Kenny was born and raised in Syracuse, New York, the son of Theresa Bridget (Donigan) and Paul Austin Kenny. As a young child, he loved drawing and collecting record albums in the late 1960s and '70s. He went to Bishop Grimes High School, a Catholic high school, which is also located in Syracuse. He was friends with comedian Bobcat Goldthwait when they were in school after Bobcat got in trouble with one of the teachers in the school, who dragged him into Kenny's class. The two were friends through school and after college and appeared in films that Bobcat directed and starred in such as Shakes the Clown and World's Greatest Dad.
In addition to SpongeBob, Tom Kenny has voiced many characters in over 200 productions. Kenny said that he voices "a lot of sweet yellow characters for some reason." He described his perspective on SpongeBob's voice in an interview: "He's not quite an adult, he's not quite a kid. Think a Stan Laurel, Jerry Lewis kind of child-man. Kind of like a Munchkin but not quite, kind of like a kid, but not in a Charlie Brown child's voice on the TV shows."
He is known to provide the voice of the various meows of Gary the Snail in SpongeBob, but he played his first set of voice actor roles for Rocko's Modern Life, primarily as Heffer Wolfe. Joe Murray auditioned Kenny for voice acting roles for the series in a casting call in Los Angeles, California. On one occasion, the producers required Kenny to fill the role of Charlie Adler, who was absent. In addition, Kenny had to perform one song and learn how to play another song within ten minutes due to time constraints. He said that this helped him believe that he could stand "toe to toe" with other voice actors. He also voices Cupid for the Nickelodeon show The Fairly OddParents.
Joe Murray chose Kenny for a voice acting position in Camp Lazlo as Lumpus and Slinkman, because Murray, after seeing Kenny's previous work for Rocko's Modern Life, felt that Kenny "adds writing to his roles" and "brings so much".
Kenny speaking at the Foster's Home for Imaginary Friends panel at the 2007 San Diego Comic Con He voiced Dog in CatDog, as well as the voice of Cliff. He also had a few roles in The Powerpuff Girls TV show. He was the Mayor, the Narrator, Mitch Mitchelson, Snake, and Little Arturo from the Gangrene Gang, Rainbow the Clown, etc. He voiced Eduardo, and various other characters in Foster's Home For Imaginary Friends. He played Dr. Two-Brains in the PBS Kids show, WordGirl He plays a number of roles in the Transformers Animated TV show. A few of the characters he voices in this series are Starscream and his clones, Isaac Sumdac and Waspinator. Kenny also voiced several characters on the animated show Xiaolin Showdown, as well as the Autobots Skids and Wheelie in the live-action Transformers film series. He has voiced The Penguin on The Batman, as well as Mumbo Jumbo on Teen Titans. On Dilbert, Kenny voiced Ratbert, Asok and other one-time characters. He played Mr. Hal Gibson in the animated kids show Super Robot Monkey Team Hyper Force GO! He is also Yancy Fry and various minor characters on Futurama. He is the voice of The Ice King and Magic Man on Adventure Time.
Kenny at the 2009 San Diego Comic Con In 2009, Kenny became a regular cast voice in the Fox comedy series Sit Down, Shut Up. He voices Muhammad Sabeeh "Happy" Fa-ach Nuabar, the secretive custodian who is plotting a terrorist attack, as well as Happy's interpreter. The series premiered on April 19, 2009. Kenan Thompson, Kristin Chenoweth, Jason Bateman, Nick Kroll, Cheri Oteri, Henry Winkler, Will Arnett, and Will Forte are the other main cast members.
In 2011, Kenny starred as the voice of Rabbit in Winnie the Pooh.
Since 2012, Kenny has been voicing Woody Johnson on Comedy Central's Brickleberry.
In 2014, he voices Flain, Seismo, and Teslo in Mixels. He voices Sumo in the new Cartoon Network show, Clarence.
He has also provided voices in television advertisements for Best Buy (as an elf for a Christmas spot). and Experian (as a talking modem alongside DC Douglas)
Kenny first met his wife Jill Talley in 1992 while working on The Edge. The two have since frequently collaborated on SpongeBob among other works. They have two children, Mack (born c. 1997) and Nora (born August 2003).