Background: The purpose of the present study was to examine, through an experimental vignette design, the effects of appearance-related comments from one’s partner on body image and the perceived quality of one’s relationship. Body image was considered both in negative (body dissatisfaction) and positive (body compassion) terms. Methods: Appearance-related commentary from one’s partner was manipulated through a vignette describing the purchase of a swimsuit. The participants (n = 211) were women and men who were randomly assigned to one of the three experimental conditions (positive comment, negative comment, no comment). Results: A series of ANOVAs showed different findings for women and men. Being criticized for body weight and shape caused an increase in body dissatisfaction and a decrease in body compassion in men but not in women. Regarding couple satisfaction, women who imagined receiving a compliment about their body perceived being more accepted by their partner and were less afraid of being abandoned or rejected. Conclusions: Our findings highlight the importance of appearance-based comments from one’s partner on men’s body image and on women’s perception of their couple relationship. Therefore, appearance comments might be addressed by interventions aimed at enhancing positive body image, reducing body dissatisfaction, and fostering couple relationships, carefully considering sex differences.