Aims Theory of Mind (ToM) is an important component of social cognition. Deficits in ToM are found in various neurodevelopmental disorders and social and environmental factors have been found to influence ToM development. Little previous research has focused on effects of exposure to toxins; this report examines the impact of tobacco. Place of Study Department of Psychiatry, University of Colorado School of Medicine, between April 2006 – August 2012. Methodology 101 children, 18 with prenatal exposure to tobacco, underwent ToM testing at 40 (n=89) and 48 (n=77) months of age. Test questions received dichotomous pass/fail scores and percentage of correct responses was utilized as the primary dependent variable. Results At 40 months of age children were rarely able to correctly answer false belief questions and there were no significant differences according to prenatal tobacco exposure. At 48 months of age, there was a significant effect of prenatal tobacco exposure with non-exposed 48-month-olds correctly answering 45±40.6% of content false belief questions correctly, compared to 13.9±25.3% for 48-month-olds with prenatal tobacco exposure (F=4.79, df= 1,73, p=.032) Conclusion ToM abilities are rapidly developing between 40 and 48 months of age. Prenatal exposure to tobacco is associated with impairment at 48 but not 40 months of age. This finding supports consideration of nicotinic mechanisms as contributors to early development of social cognition.