On release, Chris Welch of "Melody Maker" declared: "Instant hit! John Lennon is singing better than ever. With a beautiful rock 'n' roll echo chamber on his mean but meaningful vocals and some superb drumming, it makes up the Plastics' best piece of boogie yet." "Record World" listed the song first on its three "Single Picks of the Week" predictions, saying: "John Ono Lennon is now produced by Phil Spector. 'Instant Karma' ... is gonna get YOU." "Cash Box" predicted the same success, saying: "'Instant Karma' has made it to New York, full reverb blaring and Lennon's guts pouring out in a most exciting and involving manner. The song tears out with a '50s shuffle style that really makes it." Writing in the "NME" in 1975, Charles Shaar Murray wrote of the song's "volcanically desperate optimism" and rated it "a classic". Shaar Murray added, with reference to "Cold Turkey" also: "I can't remember anybody else who put out two such utter killers in a row over the same period of time."