The New York Times opens by saying it's
a deeply sincere, elliptical movie about being and nature, men and women, self and other, worms and pigs" and concludes with this: "With its fragmentation and mysteries, “Upstream Color” offers itself up as a puzzle as well as a philosophical toy that you can spin and spin until the cafe closes and kicks you into the night.The Guardian calls it "invigoratingly freaky and strange, with a Death-Valley-dry sense of humour somewhere underneath". Slate offers a FAQ.
Empire Online concludes,
How to sum up? You have to make synapse-spark connections, interpret events to your own satisfaction, pick up visual cues (a long stretch of the film is dialogue-free) and be happy with not knowing all the answers (you know, like in life — but not in most motion pictures). A perfectly judged, strikingly beautiful film, but also a lunatic enterprise which invites — even welcomes — befuddlement as much as wonder. A true original.Roger Ebert's site says it "might be described as an oblique romantic science-fiction mystery thriller" and that it "one of those movies that you either give yourself over to or resolutely resist. If not understanding something annoys you, you will struggle against it or simply disengage." Rotten Tomatoes has a critics rating of 86%.