This study examined parenting knowledge among Mexican‐origin adolescent mothers (N = 191; Mage = 16.26 years), family contextual factors associated with adolescents' parenting knowledge, and toddlers' (Mage = 2.01 years) subsequent developmental outcomes. Data came from home interviews and direct child assessments. Adolescents both underestimated and overestimated children's developmental timing, and showed differences in their knowledge of specific developmental domains. Instrumental support from mother figures was positively linked to adolescents' knowledge accuracy, whereas emotional support was negatively related to adolescents' knowledge confidence. Furthermore, whereas mother figures' autonomy granting was positively linked to knowledge confidence, psychological control was associated with less accurate adolescent parenting knowledge. Toddlers of adolescents with more accurate knowledge showed positive developmental functioning. Intervention implications are discussed.