Inspired by the story of singer Steve Tilston, who learned of the existence of a letter that John Lennon had written to him 34 years after the letter was written.
The "Danny Collins" concert footage at the beginning of the film was shot at a Los Angeles concert by the band Chicago.
Dan Fogelman had Pacino in mind to play Danny Collins while writing the script. Pacino agreed, with only one request, that Bobby Cannavale play his son.
The audience used was from a Chicago concert. The band took a 15 minute break while Pacino and crew did their thing.
The pictures on the wall of Collins' house (around 10 mins in), are all pics from previous Pacino roles; The Godfather, Serpico etc.