Young children are an important focus of sun-protection efforts, but there has been relatively little study of sun-protection interventions developed for preschool-aged children and their parents. This paper reports on the evaluation of Sun Protection is Fun! (S.P.F.), designed to improve parents' practices and psychosocial outcomes related to protecting preschool children from sun exposure. A group-randomized trial was conducted in 20 preschools to evaluate the S.P.F. parent intervention that included a video, newsletters, and handbooks. A separate, on-site intervention for preschool staff aimed to create a preschool climate that encouraged parents' sun protection for their children. Cross-sectional samples of parents completed surveys at baseline ( n = 384), 12 months ( n = 640), and 24 months ( n = 694). S.P.F. demonstrated significant effects on parents' sun-avoidance strategies at 12 months ( P < .05) and sunscreen use at 24 months ( P < .05). There were significant intervention effects on parents' sun-protection knowledge ( P < .001), perceived norms of teachers' sunscreen use ( P < .001), sunscreen impediments ( P < .05), and sunscreen expectancies ( P < .05) at 12 months. Parents' perceived norms of teacher sunscreen use were significantly improved at 24 months ( P < .001). More intense intervention strategies may need to complement take-home materials to result in greater effects on parents' sun protection for their children.