Objective—The present study examined (a) the interactions between early behavior, early parenting, and early family adversity in predicting later ODD symptoms, and (b) the reciprocal relations between parent functioning and ODD symptoms across the preschool years. Method—Participants were 258 3-year-old children (138 boys and 120 girls) and their parents from diverse backgrounds who participated in a 4-year longitudinal study. Results—Early child behavior, parenting, and family adversity did not significantly interact in the predicted direction. Reciprocal relations between ODD symptoms and parent functioning were observed for maternal and paternal depression, and maternal warmth. Paternal laxness at age 4 predicted ODD symptoms at age 5 and paternal laxness at age 5 predicted ODD symptoms at age 6, but child ODD did not significantly predict paternal laxness. Conclusion—Results suggest that ODD symptoms may develop through a transactional process between parent and child functioning across the preschool years.