Loesser was born in New York City to Henry Loesser, a pianist, and Julia Ehrlich. He left City College of New York in 1925 after one year. After trying various jobs, by 1935 he was performing in a club with singer Lynn Blankenbaker Garland, whom he married in 1936.
In 1944, Loesser worked on a little known musical intended to be performed by and for US soldiers abroad, titled Hi Yank!, the music for which was composed by Alex North. Hi Yank! was produced by the U.S. Army Office of Special Services as a "blueprint special" to boost the morale of soldiers located where USO shows could not visit. The "blueprint" was a book containing a musical script with instructions for staging the show, using materials locally available to deployed soldiers. A document located at the US Army Centre for Military History states, "A touring company has been formed in Italy to tour a production of "Hi, Yank!"".
This unique Hi Yank! show without stars or a conventional theater run was generally forgotten until 2008, when the PBSHistory Detectives TV show researched the case of a long-saved radio transcription disc. The disc has two songs and a promotional announcement for the show's Fort Dix premiere in August 1944, when the disc was broadcast there.
Another unproduced musical, Señor Discretion Himself, premiered after his death. He started working on a musical version of the Budd Schulberg short story Señor Discretion Himself in 1966, but stopped working on it after 2 years. A version was presented in 1985 at the New York Musical Theatre Works. With the support of Jo Loesser, a completed version was presented at the Arena Stage, Washington, DC, in 2004, reworked by the group Culture Clash and director Charles Randolph-Wright.
Loesser was divorced from his first wife, Lynn, in 1957. They had two children together: John Loesser and Susan Loesser, an author who wrote her father's biography A Most Remarkable Fella: Frank Loesser and the Guys and Dolls in His Life: A Portrait by His Daughter (1993, 2000).
He married his second wife Jo Sullivan (born Elizabeth Josephine Sullivan) on April 29, 1959. Loesser was introduced to Jo by his first wife Lynn. Jo Sullivan had played a lead in The Most Happy Fella. They had two children, Hannah and Emily. Emily is a performer who is married to Don Stephenson.
"Baby, It's Cold Outside" from the M-G-M picture "Neptune's Daughter" (1949). This was originally a song which Loesser and his wife Lynn performed at parties for the private entertainment of friends. They also recorded the song for Mercury Records. Under contract to Metro-Goldwyn-Mayer to supply a full score for Neptune's Daughter, Loesser included this song which he had created in 1944, originally for their housewarming party.
"Heart and Soul" (from the Paramount short subject A Song is Born) – lyrics