While making this film, Frank Sinatra took an almost immediate dislike to Doris Day's husband, Martin Melcher, thought that Melcher was using her to get ahead in the movie business and tried to convince Day of that fact. After Day refused to listen to Sinatra's advice, he had Melcher banned from the set. After Melcher's death in 1968, it was discovered that he had squandered all the money Day had earned during her 20-year film career.
Ethel Barrymore was very old and feeble during the filming and spent most of her time between takes in a wheelchair. She was not disabled but was getting frail and had to conserve her energy for her onscreen performance. Frank Sinatra threw a surprise birthday party for her on the set, a gesture that clearly moved and touched her.
The initial idea in filming "One for My Baby" was to illustrate Barney's hopeless anonymity by having the unruly bar crowd all but drown out his performance of the song, but Frank Sinatra's vocal was so powerful that director Gordon Douglas decided to gradually decrease the ambient noise until only Sinatra's voice could be heard. This turns the song into an internal monologue, as if Barney is blocking out the crowd's noise and singing to himself.
Doris Day wrote that Frank Sinatra disliked Day's husband/manager Martin Melcher so much that he threatened to walk off this film unless Melcher was banned from the Warner Brothers lot during production. Jack L. Warner issued this order to all studio security guards so that production would not be shut down.
The film was untitled until Frank Sinatra's "Young at Heart" became a smash hit and was tagged onto the opening credits.