Lowdermilk’s most recent musicals have been collaborations with Kait Kerrigan. Their collaborations include The Woman Upstairs, The Unauthorized Autobiography of Samantha Brown (with Zach Altman) and Wrong Number. Lowdermilk and Kerrigan wrote TheaterworksUSA's adaptation of Henry and Mudge, which premiered Off-Broadway in 2006 at the Lucille Lortel Theatre. In one review of that piece, Lowdermilk and Kerrigan were called "perhaps the most important young writers in musical theatre today."
Lowdermilk has received a Richard Rodgers Staged Reading Award from the American Academy of Arts and Letters, an Alan Menken scholarship award from NYU Steinhardt, and a Jonathan Larson Memorial Fellowship at the Dramatists Guild.
In 2011, Kerrigan and Lowdermilk released their first CD, "Our First Mistake". The CD was a result of fan support through a campaign on Kickstarter. To celebrate both the CD and their fans, Kerrigan-Lowdermilk launched a series of New York City concerts under the name You Made This Tour. A selection of recordings from these concerts was bundled for their follow-up album, "Kerrigan-Lowdermilk Live".
The pair made their London debut at the St James Theatre in February 2014 in a concert series produced by United Theatrical - a London-based theatrical production company run by Stuart Matthew Price and James Yeoburn. The featured singers included West End performers Rachel Tucker, Julie Atherton, Daniel Boys, Chloe Hart, Jodie Jacobs, Lauren Samuels and Anton Zetterholm. 
- Battleship Ticonderoga (book by Brian Lowdermilk and Marcus Stevens)
- Cellular Passion
- Elliot and the Magic Bed (lyrics by Brian Lowdermilk and Marcus Stevens; book by Marcus Stevens)
- From Where I Stand
- Henry and Mudge (with Kait Kerrigan)
- Places You Never Called Home
- RED (lyrics by Brian Lowdermilk and Marcus Stevens; book by Marcus Stevens)
- Room To Grow
- Transient Days (book by Zach Altman)
- The Unauthorized Autobiography of Samantha Brown (music and lyrics by Brian Lowdermilk; book and lyrics by Kait Kerrigan; additional book and concept by Zach Altman); (2009) is a musical written jointly by Kait Kerrigan and Lowdermilk. Kerrigan initially wrote the musical for an all student production at Barnard College but later re-worked the musical with the assistance of Lowdermilk for a wider audience. The plot involves the upcoming graduation of high school class valedictorian, Samantha, who must decide what she wants with her life and how her parents, her friends, and her boyfriend, Adam, fit into her life.
- Tales from the Bad Years (with Kait Kerrigan)
- Whatever It Takes (book by Brian Lowdermilk and Gary Sunshine; book by Gary Sunshine)
- The Woman Upstairs (with Kait Kerrigan)
- Wrong Number (with Kait Kerrigan)
- Our First Mistake (Kerrigan & Lowdermilk)
- Graeber, Laurel (2007-01-05). "SPARE TIMES: Jan. 5 - Jan. 11; HENRY AND MUDGE". The New York Times (The New York Times Company). Retrieved 2008-05-01.
- Murray, Matthew (2006-12-17). "Off Broadway: Not Your Grandma's Theatre - Henry and Mudge". Talkin Broadway. www.TalkinBroadway.Org, Inc. Retrieved 2008-05-01.
- "Academy Awards". American Academy of Arts and Letters. Archived from the original on 2008-03-06. Retrieved 2008-05-01.
- Maureen Belluscio (September 24, 2004). "Broadway prodigy hits the big time". Washington Square News. Retrieved 2008-05-01.[dead link]
- "Kait Kerrigan-Brian Lowdermilk to Make U.K. Debut at London's St. James Studio; Guests to Include Rachel Tucker". 2014-01-24.
- "'Samantha Brown,' a musical in the making". LA Times. 22 April 2009. Retrieved 9 January 2014.
- "Andrew Durand, Meghann Fahy, Stephen Bogardus Populate Goodspeed's 'Samantha Brown'". Yahoo. Retrieved 9 January 2014.
- "Andrew Durand, Meghann Fahy, Stephen Bogardus Populate Goodspeed's Samantha Brown". Playbill. Retrieved 9 January 2014.