The song is sung all the way through once in the musical by Don Quixote as he stands vigil over his armor, in response to Aldonza (Dulcinea)'s question about what he means by "following the quest". It is reprised partially three more times – the last by prisoners in a dungeon as Miguel de Cervantes and his manservant mount the drawbridge-like prison staircase to face trial by the Spanish Inquisition.
It was awarded the Contemporary Classics Award from the Songwriter's Hall of Fame.
During Robert F. Kennedy's long shot campaign for the presidency in 1968, Senator George McGovern introduced him before a South Dakota stump speech by quoting from The Impossible Dream. Afterwards Kennedy questioned McGovern whether he really thought it was impossible. McGovern replied, "No, I don't think it's impossible. I just... wanted the audience to understand it's worth making the effort, whether you win or lose." Kennedy replied, "Well, that's what I think." It was actually Robert Kennedy's favorite song, and Andy Williams, who recorded the song, was one of Kennedy's close friends. The song was also a favorite of younger brother Ted Kennedy and was performed by Brian Stokes Mitchell at his memorial service in 2009.