Schlesinger is a cousin of Jon Bernthal, an actor who is best known for his roles as Shane Walsh on the AMC television series The Walking Dead and The Punisher/Frank Castle in Netflix's Daredevil and The Punisher. He is also the grandson of Murray Bernthal (1911–2010), a musician and Producer, long active in Syracuse, New York.

Schlesinger was nominated for an Academy Award and a Golden Globe Award in 1997 for writing the title track of the Tom Hanks-directed film That Thing You Do! as well as two other songs for the film.

Fountains of Wayne was nominated for two Grammy Awards in 2003 for Best New Artist and Best Pop Performance by a Duo or Group with Vocal for "Stacy's Mom".

Schlesinger and The Daily Show executive Producer David Javerbaum co-wrote the songs for the musical theater adaptation of the John Waters film Cry-Baby. Cry-Baby debuted at the La Jolla Playhouse in La Jolla, California, in November 2007. Previews for the Broadway run began at the Marquis Theatre on March 15, 2008. Its official opening night was April 24, 2008.

Schlesinger's television composing work includes theme music, songs, and/or score for I Love You America (Hulu), The Maya Rudolph Show (NBC), A Colbert Christmas: The Greatest Gift of All!, the 2011 and 2012 Tony Awards, the 2011 and 2013 Emmy Awards, Big Time Rush, T.U.F.F. Puppy (Nickelodeon), Good Luck Charlie (Disney Channel), Fresh Beat Band (Nickelodeon), Kathy (Bravo), Crank Yankers, "Wedding Band" (TBS), the Billboard Music Awards, Bubble Guppies (Nick Jr.), The Howard Stern Show, Sesame Street, Comedy Central's "Night Of Too Many Stars", Robert Smigel's cartoons for Saturday Night Live, The Disney Parks Christmas Day Parade with Neil Patrick Harris, the Comedy Awards (Comedy Central), American Dreams, Stephen King's Kingdom Hospital, The In-Laws, The Man Show, Too Late with Adam Carolla, The Dana Carvey Show, John Leguizamo's House Of Buggin', My Kind of Town, and others. His songs have also been licensed for use on numerous television series including Scrubs, The Hills, Gossip Girl, Melrose Place, Felicity, Roswell, and others.

Schlesinger is also in a side project band called Tinted Windows formed by Guitarist James Iha, previously of The Smashing Pumpkins and A Perfect Circle, singer Taylor Hanson of Hanson, and Bun E. Carlos of Cheap Trick. This new project will run alongside all the artists' main bands. He also contributed to Iha's second solo album, Look to the Sky (2012).

Schlesinger received a 2013 Daytime Emmy nomination for Outstanding Original Song for his "Elmo The Musical" theme for Sesame Street. He and Molly Boylan received a 2011 Daytime Emmy nomination for the song "I Wonder" from Sesame Street.

Schlesinger and Javerbaum co-wrote the closing song "I Have Faith In You" for Javerbaum's play An Act Of God which opened on Broadway on May 28, 2015. The song is performed by Jim Parsons, Chris Fitzgerald, and Tim Kazurinsky.

Schlesinger received two 2016 Emmy nominations for his work on the CW series Crazy Ex-Girlfriend: Outstanding Original Music and Lyrics for "Settle For Me" (co-written with Rachel Bloom and Jack Dolgen), and Outstanding Main Title Theme (co-written with Rachel Bloom).

He received a 2017 Emmy nomination for Outstanding Original Music and Lyrics for "We Tapped That Ass" (co-written with Rachel Bloom and Jack Dolgen) from the CW series Crazy Ex-Girlfriend.