"Repulsive, socially unredeemable waste of celluloid... Filmed for no apparent reason except to offend and appall."
– Leonard Maltin, Movie and Video Guide

"An oddly compelling study of family pathology with blackly comic undertones, in the tradition of Wes Craven's The Hills Have Eyes [1977] and Tobe Hooper's The Texas Chainsaw Massacre [1974]...Carradine and Smith make an unexpectedly engaging couple, and the supporting work is all strong. Sonny Boy is a heady, offbeat mix of myth, social drama, and psychological thriller that is added testimony to the creative vitality to be found in the B-movie fringe."
– TV Guide

"Sonny Boy is one of the most demented, sick minded, and just plain bizarre movies I have ever seen. I loved every minute of it, from the warbling of David Carradine during the opening credits, to the final freeze-frame... Maybe the movie is a mess, but if it is, everything is messed up in a way so that it comes together brilliantly. At the very least, I consider the movie a flawed masterpiece."
– The Unknown Movies

"A completely unique art-sleaze masterpiece that should be remembered as the cult film of the decade...falls somewhere between Paris, Texas [1984] and Pink Flamingos [1972]."
– The Cutting Edge

"A demented lo-fi tumble into dark surrealism... Perhaps best described as a dark fairy tale, Sonny Boy's skewed approach to its frequently unpleasant subject matter keeps viewers off-balance. Filtering action through Sonny's childish, warped perspective and bits of abstract narration, the most vicious of acts are lent a dreamlike, idyllic quality very much at odds with reality... the sort of considered, artful filmmaking people should have the chance to experience without trekking to the ends of the earth, or at least the grotty corners of swap meets."
– Twitch

"All of the actors are excellent. Not just a sick exploitation movie, Sonny Boy has many inspired, funny, and surprising moments. Even the simple desert set is great and could have been inspired by old Krazy Kat comics."
– Psychotronic Magazine