Ordinary variations in human infants’ attachment behaviors – their proclivity to seek and accept comfort from caregivers – are associated with a wide range of individual differences in psychological functioning in adults. The current investigation examined variation in the oxytocin receptor ( OXTR) gene as one possible source of these variations in infant attachment. One hundred seventy-six infants (77 Caucasian, 99 non-Caucasian) were classified as securely or insecurely attached based on their behavior in the Strange Situation (Ainsworth et al., 1978). The A allele of OXTR rs2254298 was associated with attachment security in the non-Caucasian infants ( p < 0.005). These findings underscore the importance of oxytocin in the development of human social behavior and support its role in social stress-regulation and the development of trust.