Background Callous‐unemotional behaviors identify children at risk for severe and chronic antisocial behavior. Research is needed to establish pathways from temperament and parenting factors that give rise to callous‐unemotional behaviors, including interactions of positive versus harsh parenting with child fearlessness. Methods Multimethod data, including parent reports and observations of parent and child behavior, were drawn from a prospective, longitudinal sample of low‐income boys (N = 310) with assessments at 18, 24, and 42 months, and at ages 10–12 years old. Results Parent‐reported callous‐unemotional, oppositional, and attention‐deficit factors were separable at 42 months. Callous‐unemotional behaviors at 42 months predicted callous‐unemotional behaviors at ages 10–12, accounting for earlier oppositional and attention‐deficit behaviors and self‐reported child delinquency at ages 10–12. Observations of fearlessness at 24 months predicted callous‐unemotional behaviors at 42 months, but only when parents exhibited low observed levels of positive parenting. The interaction of fearlessness and low positive parenting indirectly predicted callous‐unemotional behaviors at 10–12 via callous‐unemotional behaviors at 42 months. Conclusions Early fearlessness interacts with low positive parenting to predict early callous‐unemotional behaviors, with lasting effects of this person‐by‐context interaction on callous‐unemotional behaviors into late childhood.