The current study examined the relation between parental expressed emotion, a construct of the quality and amount of emotion expressed within the family environment that is a well-established predictor of symptom relapse in various psychological disorders, with externalizing behaviors in children and adolescents with an autism spectrum disorder (ASD). Participants were 111 parents of 6- to 18-year-old children and adolescents with an ASD who completed questionnaires measuring family environment variables (including parental expressed emotion, parental distress, and parenting practices), as well as assessing their child’s autism symptoms and emotional and behavioral functioning. Results of regression analyses indicated that parental expressed emotion, specifically criticism/hostility, accounted for 18.7% of the variance in child externalizing behaviors beyond that accounted for by demographic control variables, overinvolvement, parental distress, and parenting practices. Findings highlight a possible point of intervention for parents of children and adolescents with an ASD with concomitant externalizing behaviors.