The present study was designed to examine the relations between parental pessimism and peer relations and health in preschool children and to examine the role that child positive and negative affect played within this relationship. Thirty-seven mothers and their children (mean age = 48.1 months) volunteered from local preschools and daycares within a mid-sized Atlantic Canadian city. Mothers completed the Generalized Expectancy for Success Scale--Revised, as well as the Positive and Negative Affect Schedule and a brief demographic questionnaire. Teachers completed the Preschool Play Behaviour Scale. Results revealed significant correlations between parental pessimism and child affectivity and social play, and between child affectivity and various types of play behavior. Significant interactions were also found between parental pessimism and child affectivity in the prediction of social play behavior. Results are discussed in terms of the importance of parental attitudes to a child's social and physical well-being. (Contains 1 note.)