Mutual antipathies are characterized by reciprocated disliking. The current study identifies behavioral attributes that forecast participation in mutual antipathies. Participants were 313 (170 girls, 143 boys) Florida public school students (9–14 years old; Mage = 11.09, SDage = 0.90) who thrice nominated disliked classmates during a single school year (approximately 6.5 weeks apart). Behavioral attributes assayed in the fall semester identified those currently involved in mutual antipathies (N = 101 dyads) and those prospectively involved in new mutual antipathies (N = 124 dyads). Youth involved in existing and new mutual antipathies were characterized by (a) low peer-reported academic achievement and prosocial behavior (prospective only, p = 0.06), (b) high peer-reported disruptiveness and aggression, and (c) high self-reported emotional problems (concurrent only) and emotional reactivity (prospective only). Thus, youth who behave in unattractive ways are disliked and they tend to return the sentiment.