 Among Lennon's biographers, Ben Urish and Kenneth Bielen view "Instant Karma!" as "a chiding though positive message for humanity", while Jon Wiener praises Lennon's "rich, deep voice" on a recording where the sound is "irresistible". Philip Norman describes the song as "similar to 'Cold Turkey' in tempo but far more relaxed and humorous", adding that Spector's production gave Lennon's voice "a taut expressiveness it had not had since 'Norwegian Wood'". While noting the significance of the session for George Harrison's career, author Simon Leng praises the recording as being "full of urgency and sheer excitement".
