Using a sample of biological resident fathers and their children from the Early Childhood Longitudinal Study Birth Cohort (ECLS-B) 9- and 24-month surveys (N = 5,300), this study examines associations and the direct and indirect pathways through which men's pregnancy intentions influence toddlers' mental proficiency and attachment security. Findings indicate that unwanted and mistimed pregnancies for fathers had negative consequences for toddlers' mental proficiency and attachment security. Additionally, men's pregnancy intentions were found to work indirectly through lower prenatal behaviors and father engagement and greater mother-father relationship conflict to negatively influence toddlers' mental proficiency. Men's pregnancy intentions also worked indirectly through greater relationship conflict and higher father involvement to influence attachment security.