Bart Howard, the composer of ''Fly Me to the Moon'' and of cabaret songs recorded by Mabel Mercer, Johnny Mathis and many others, died on Saturday in Carmel, N.Y. He was 88 and lived in North Salem, N.Y.

The cause was complications from a stroke, said his companion of 58 years, Thomas Fowler.

Mr. Howard's signature song, originally titled ''In Other Words,'' was introduced in 1954 by the cabaret singer Felicia Sanders. Its popularity spread after Peggy Lee sang it on ''The Ed Sullivan Show'' in 1960, and it became a bona fide hit in a 1962 bossa nova instrumental version by Lee's conductor, Joe Harnell.

''I've always said it took me 20 years to find out how to write a song in 20 minutes,'' Mr. Howard recalled in an interview with The New York Times in 1988. ''The song just fell out of me. One publisher wanted me to change the lyric to 'take me to the moon.' Had I done that I don't know where I'd be today.''

Born Howard Joseph Gustafson in Burlington, Iowa, Mr. Howard left home at 16 to be a pianist in a dance band that toured with the Siamese twins Daisy and Violet Hilton. Hoping to write songs for the movies, he traveled to Los Angeles in 1934 and ended up accompanying a female impersonator, Rae Bourbon. He moved to New York after teaming with Elizabeth Talbot-Martin, a comedian and impersonator who was booked at the Rainbow Room in 1937.