Levant was born in Pittsburgh, Pennsylvania, United States, in 1906, to Orthodox Jewish Max, a watchmaker, and Annie, who emigrated from Russia.

During this period, he also wrote or co-wrote numerous popular songs that made the hit parade, the most noteworthy being "Blame It on My Youth" (1934), now considered a standard.

[6] These formal studies led to a request by Aaron Copland to play at the Yaddo Festival of contemporary American music on April 30 of that year.

Levant made his debut as a music conductor in 1938 on Broadway, filling in for his brother Harry in sixty-five performances of George S. Kaufman and Moss Hart’s The Fabulous Invalid.

Kieran praised Levant as having a "positive genius for making offhand cutting remarks that couldn't have been sharper if he'd honed them a week in his mind.

"[9] Examples include "I knew Doris Day before she was a virgin," "I think a lot of [conductor/composer Leonard] Bernstein—but not as much as he does," and (after Marilyn converted to Judaism when she married playwright Arthur Miller), "Now that Marilyn Monroe is kosher, Arthur Miller can eat her.” [10][11][12] Levant appeared in feature films, starting from the 1920s until the mid-50s, often playing a pianist or composer.

[13] Oscar Levant regularly appeared on NBC radio's Kraft Music Hall, starring singer Al Jolson.

Actor John Garfield used Levant as a model when creating the character of troubled genius Mickey Borden in the 1938 film Four Daughters.

[24] In April 2023, a play about Levant's life written by Pulitzer Prize winner Doug Wright premiered on Broadway.

[25] Good Night, Oscar was a fictionalized version of a true event in Levant's life, when he was given a four-hour furlough from a psychiatric hospital to allow him to appear on The Tonight Show.