"Primer" received positive reception from critics. Rotten Tomatoes gave the film a 72% approval rating based on 129 reviews, with an average rating of 6.6/10. The consensus reads, "Dense, obtuse, but stimulating, "Primer" is a film ready for viewers ready for a cerebral challenge." The site also listed "Primer" as one of the best science fiction films "for the thinking man". On Metacritic, the film holds a score of 68 out of 100 based on reviews from 25 critics, indicating "generally favorable reviews".