
On Rotten Tomatoes, the film has an approval rating of 85% based on 103 reviews, with an average rating of 6.8/10.

It ended up grossing $3.8 million, finishing 8th at the box office. Megan Leavey was released alongside It Comes at Night and The Mummy and was expected to gross around $3 million from 1,956 theaters in its opening weekend. In the UK and Australia the film was released on DVD as Rex. The film was released on DVD and Blu-ray on September 5, 2017, from Universal Studios Home Entertainment. In January 2017, Bleecker Street acquired distribution rights to the film and set it for release on June 9, 2017. Principal photography on the film began on Octoin Charleston, South Carolina, including scenes filmed at The Citadel, with other scenes filmed in Georgia and New York City, with extensive desert and combat scenes shot in Spain. The script was written by Pamela Gray, with the help of Annie Mumolo, Tim Lovestedt, and Jordan Roberts. On August 7, 2015, it was announced that Gabriela Cowperthwaite would be directing a film about Megan Leavey, to be portrayed by actress Kate Mara, and her military combat dog Rex.

The real Megan Leavey is credited in the role of Female Drill Instructor #3, while Rex is portrayed by Varco, in an uncredited role. Edie Falco as Jackie, Megan's overbearing mother.Will Patton as Jim Leavey, Megan's stepfather.Bradley Whitford as Bob Leavey, Megan's estranged father.
