Cognitive confidence, a type of metacognition referring to confidence in one's cognitive abilities (e.g., memory, perception, etc.), has been identified as relevant to eating disorders (EDs) using self-report measures. Repeated checking has been found to elicit decreases in perceptual confidence in obsessive compulsive disorder (OCD). The purpose of the present study was to experimentally investigate perceptual confidence, a type of cognitive confidence, in EDs. Specifically, this construct was investigated in the context of body checking, a behaviour with similarities to compulsive checking as observed in OCD. Women with bulimia nervosa (BN; n = 21) and healthy controls (HC;n = 24) participated in the study. There were no group differences with regards to perceptual confidence at baseline F(1, 43) = 0.5, p = 0.48, ηp2 = 0.01, but a significant difference was observed post-checking F(1, 43) = 7.79, p = 0.008, ηp2 = 0.15, which was accounted for by significant decreases in perceptual confidence in the BN group F(1, 43) = 13.31, p < 0.001, ηp2 = 0.24. Similar to compulsive checking in OCD, body checking may paradoxically decrease confidence regarding one's appearance. LEVEL OF EVIDENCE: Level I, experimental study.