Amazon Prime Video released the action blockbuster on Friday (2 July), with many people watching it over the weekend.
The time-travel movie, which was panned by critics, received a much warmer reception from audiences.
It follows a family man who is drafted to fight in a future war where the fate of humanity relies on his ability to confront the past.
While some praised Chris McKay’s film for having a “concrete ending” that didn’t appear set up a sequel, others felt it to be too derivative of other films, including Alien, Prometheus and even Twilight: Eclipse.
“The last act is a straight up copy of Alien,” one viewer complained.
Others commented that the film seemed to reach a natural conclusion – but then continued for another 40 minutes, which lessened what had come before.
“The Tomorrow War is one of those movies which has a pretty obvious, satisfying ending like 95 minutes in... and then just *continues* for another 40 uninteresting minutes,” one viewer added.
Someone else commented: “The ending is simply one of the most ridiculous things you will ever see.”
The Tomorrow War, which also stars The Handmaid’s Tale star Yvonne Strahovski and JK Simmons, is available to stream on Amazon Prime Video now.