Marienthal attended the Berklee College of Music for two years, and earned a Berklee Distinguished Alumnus Award for outstanding achievements in contemporary music. Following his departure from Berklee, he went on tour for seven months and played live in New Orleans for just under five years as a member of Al Hirt's band. Marienthal moved to Los Angeles in 1980 after his tenure with Hirt, and auditioned for the Disneyland Band. He got the gig, and worked full-time as both a staff member at Disney and a studio and live musician.

In 1986, he met Chick Corea, and soon thereafter earned a spot in Corea's Elektric Band. He recorded six albums and made several world tours as a member of that group. He also landed his own recording contract with GRP during this period. His first date as a leader was Voices of the Heart in 1988, which was produced by Corea. Marienthal's next two offerings, 1989's Round Trip and 1990's Crossroads, were co-produced by himself and fellow Elektric Band member John Patitucci. This was a busy period for Marienthal: he became a regular GRP studio musician in addition to his Elektric Band membership, and toured with the GRP All-Star Big Band, Lee Ritenour's and David Benoit's bands, and his own group. He enlisted the help of Jeff Lorber and Russell Ferrante for 1991's Oasis. The album was his most successful to that point; it placed in the Top Five of the contemporary jazz charts, and two of its tracks placed in the Top Ten of the national contemporary jazz radio charts. Lorber produced two more GRP dates for Marienthal, 1993's One Touch, and 1994's Street Dance.

Marienthal left GRP for Ritenour's new Verve-distributed imprint ie: Music. The guitarist produced Easy Street for release in 1997; its title track was a hit at contemporary jazz radio. His next offering as a leader for the label was 1998's Walk Tall, a heartfelt tribute to Cannonball Adderley. Produced by Harvey Mason, the single "Here in My Heart" stayed at number one on the national Contemporary Jazz charts for three weeks, and a cover of Adderley's classic "Mercy, Mercy, Mercy" reached number five.

Marienthal spent the next five years as a studio and touring musician with various acts, including being the lead alto player in composer Gordon Goodwin's Big Phat Band. He also served as the musical director of an annual fundraising concert for High Hopes, the California non-profit organization those who have suffered traumatic head injuries.

In 2002, Marienthal signed with Rippington member Russ Freeman's Peak label. There he recorded four albums: 2003's Sweet Talk, 2005's Got You Covered (leading an all-star band through a collection of cover tunes), 2007's Just Around the Corner, and 2011's Turn Up the Heat; the latter featured Robben Ford and Lorber. In 2012, Marienthal's It's Love was released on eOne Entertainment, on the very same day as Lorber's revamped Jeff Lorber Fusion's Galaxy was released; the saxophonist is a member of that band. ~ Thom Jurek