Benmont Tench was born in Gainesville, Florida, the second child of Benjamin Montmorency Tench, Jr. and Mary Catherine McInnis Tench. His father was born and raised in Gainesville, and served as a circuit court judge.
Benmont Tench played piano from an early age and his first recital was at age six. After discovering the music of The Beatles, he ended his classical piano lessons and focused on rock and roll. He met Tom Petty for the first time at a Gainesville music store when he was 11. Petty and Tench played together as members of the Sundowners in 1964. The Tenches' garage was a frequent practice site for the band on evenings when Benmont's father was out for the evening. Benmont's mother enjoyed having the boys there, but she would check with the neighbors to make certain the music would not disturb them.

Benmont attended Phillips Exeter Academy, and subsequently Tulane University in New Orleans. While on a college break, Tench went to a concert by Mudcrutch, Petty's band, with an opening act from nearby Jacksonville, Lynyrd Skynyrd. Afterwards, he sat in with the band on several different sessions, then went back to school. Soon after, Petty called Tench and asked him to quit school and join Mudcrutch full-time, which after long deliberation, Benmont agreed to; but before he would leave school, Petty had to convince Circuit Court Judge Benjamin Tench that his son had a promising music career.

Mudcrutch eventually evolved into Tom Petty and the Heartbreakers.
Other bands he played in include: The Apathetics, the MiffMole Band which was formed at Phillips Exeter consisting of Mike "Mudcat" Ward, currently a well-known bluesman, Rob Aberg guitarist, Doug Brown drummer, and Tuna Fish and Larry.
In addition to playing piano and Hammond organ with the Heartbreakers, Tench is also known as a skilled session musician, having recorded with dozens of notable artists, including Johnny Cash, U2, Elisa, Stevie Nicks, Lucinda Williams, Sam Phillips, You Am I, Susanna Hoffs, Bob Dylan, Roy Orbison, The Rolling Stones, Don Henley, John Prine, Ringo Starr, John Fogerty, Elvis Costello, Bonnie Raitt, Sheryl Crow, Waylon Jennings, Paul Westerberg, X, Mary Chapin Carpenter, Carlene Carter, The dB's, Alanis Morissette, The Ramones, The Screaming Trees, Warren Zevon, The Tragically Hip, The Divinyls, The Goo Goo Dolls, Green Day, The Cult, The Jayhawks, Dave Rawlings, Fiona Apple, Lone Justice, Sean Watkins, New Found Glory, Tift Merritt, Peter Case, Neil Diamond, Ryan Adams and Powderfinger, and Naughty Sweeties City of Glass.
Songs written by Tench and recorded by other artists include "You Little Thief", a top 5 UK and Australian hit for Feargal Sharkey in 1985, (written about his affair with Maria McKee, in response to her song "A Good Heart") and "Never Be You" (co-written with Petty), which became a #1 US Country hit for Rosanne Cash, also in 1985. Tench has received two ASCAP songwriting awards: in 1995 for "Stay Forever" (performed by Hal Ketchum) and in 2001 for "Unbreakable Heart" (performed by Jessica Andrews). This was also recorded by Carlene Carter in the early 1990s. He also wrote songs for Kimmie Rhodes ("Play Me A Memory") and Lone Justice ("Sweet, Sweet Baby (I'm Falling)").

In January 2008, Tench became part of a supergroup, initially named The Scrolls, now officially known as Works Progress Administration (W.P.A.). The band is composed of Tench, Sean Watkins (guitar), Sara Watkins (fiddle), Glen Phillips (guitar, vocals), Luke Bulla (fiddle), Greg Leisz (various), Pete Thomas (drums), and Davey Faragher (bass). The group released a self-titled album in September 2009. Tench penned one of the songs on the album, named "The Price," sung by Sara Watkins and himself.
In March 2009, Tench frequently appeared with the Watkins Family Hour at Largo at the Coronet in Los Angeles. He has also appeared at the Largo and at the Fillmore in San Francisco as a special guest with Gillian Welch and David Rawlings, and accompanied the Dave Rawlings Machine on part of their west coast tour in spring 2010.
On February 18, 2014, Tench released his first solo album, entitled "You Should Be So Lucky".