Prior to theatrical release, controversy arose when behind-the-scenes footage surfaced and appeared to show a distressed dog being forcibly submerged into turbulent pool water during filming. As a result of the leaked footage, the filmmakers chose to cancel the U.S. premiere. However, it was announced on February 4, 2017 by the American Humane Association that the footage was misleadingly edited and no abuse had taken place.

The dog breeds that were used in this film are: Beagle-German Shepherd-terrier mix, Golden Retriever, German Shepherd, Pembroke Welsh Corgi and St. Bernard-Australian Shepherd mix.

There is a 7 year age differences between Britt Robertson (Hannah) and KJ Apa (Ethan).

Bradley Cooper was originally slated to provide the voice of the titular dog; however, he was ultimately replaced with Josh Gad.

Britt Robertson (Hannah) and KJ Apa would later appear in I Still Believe (2020) together.

Dennis Quaid wore colored contact lenses to make his eyes brown. They are blue in real life.

Bryce Gheisar, who plays young Ethan, has a cat named Bailey in real life.

Name connection, possibly made deliberately by the filmmakers. When Bailey is reincarnated as the corgi and adopted by Maya, there is A-Ha's "Take on me" being played. The actress/model who appears in the original song video (not shown in the movie) is named Bunty Bailey.

This is Universal's first live-action family film since Big Miracle (2012).

The Maya segment of the film differs from the events in the book. In the book, Maya is a K9 officer who takes over handling Ellie after her first handler Jakob (Carlos in the film) is shot and injured by a kidnapper. In the movie, it is Ellie who is shot - fatally - by the kidnapper, then reincarnated as Tino the Corgi and adopted by Maya, a college student.

Dennis Quaid plays adult Ethan, who was once starting quarterback with a full scholarship but was injured. In Breaking Away (1979) and in Everybody's All-American (1988), Quaid played a star high school quarterback no longer playing. In Any Given Sunday (1999) he played a quarterback past his prime trying to relive his days.

The scenes where "Ellie" jumps off the bridge into the water to save the girl, and the diner Ethan and Hannah go to after the football game where Ethan's dad is drunk, are both filmed in Lockport, Manitoba.