Lombardo was born in London, Ontario, Canada,
Lombardo's compositions included the 1928 classic "Sweethearts on Parade", which was number one for three weeks in 1929 on the U.S. pop charts, "Ridin' Around in the Rain", written with Gene Austin in 1934, the jazz and pop standards "Coquette", "Boo Hoo", and "Some Rainy Day", and "Powder Your Face With Sunshine (Smile, Smile, Smile)", written with Stanley Rochinski in 1948-49. In 1927, Carmen Lombardo was the vocalist of the 1927 hit record, Charmaine, performed by the Guy Lombardo Orchestra.
As a child, Lombardo took flute lessons, and later learned to play saxophone, forming a band with his brother Guy as conductor. The band developed into The Royal Canadians in 1923, in which Carmen both sang and wrote music. He frequently collaborated with American composers and his music was recorded by Louis Armstrong, Bing Crosby, and others. Many of his compositions have also been used in Woody Allen films. When singing songs like "Alone at a Table for Two" he would allow his voice to tremble, and seem nearly to break into tears- he was caricatured in Warner Brothers cartoons as "Cryman" Lombardo.
Lombardo wrote the words and music with John Jacob Loeb for Guy Lombardo's stage productions of Arabian Nights (1954, 1955), Paradise Island (1961, 1962), and Mardi Gras (1965, 1966) at Jones Beach Marine Theater, New York.
In the late 1960s, actor-raconteur Tony Randall made several TV appearances on The Tonight Show Starring Johnny Carson in which he sang songs written by Carmen Lombardo in a voice imitating (and somewhat exaggerating) Lombardo's style. On one appearance, Lombardo and Randall performed a duet of Lombardo's "Boo Hoo (You've Got Me Crying for You)", which was one of the songs that Randall typically included in his Lombardo routine.
Lombardo died of cancer in Miami in 1971, aged 67.
Lombardo's compositions included the number one jazz and pop standard "Sweethearts on Parade", "Powder Your Face with Sunshine (Smile! Smile! Smile!)", "A Lane in Spain", "Some Rainy Day", "Boo Hoo (You've Got Me Crying For You)", "A Sailboat in the Moonlight" (1937) with John Jacob Loeb, "Coquette", written with Johnny Green and Gus Kahn, recorded by Paul Whiteman, Louis Armstrong, Jimmie Lunceford, Bud Freeman, Bob Crosby, The Ink Spots, and Fats Domino, "Seems Like Old Times", "Oahu (My Lovely Island Home)", "Get Out Those Old Records", "Ridin' Around in the Rain" with Gene Austin, "Return to Me" (1957) with Danny Di Minno, and "You're Beautiful To-Night, My Dear".
He wrote five songs for the 1934 film Many Happy Returns, in which the orchestra appeared.