The oxytocin receptor gene (OXTR) may function as a “plasticity gene” that increases or decreases sociability in those individuals susceptible to growing up in a beneficial versus more adverse environment. This study used data from 2289 (55% female) participants from the ongoing prospective Young Finns Study. Maternal emotional warmth was assessed in 1980 when the participants were 3–18years old. Participants' sociability temperament was measured at five follow-ups, from 1992 to 2012. Emotional warmth in childhood and OXTR genotype were not directly associated with temperamental sociability. We found a nominally significant gene–environment interaction (p=.03) suggesting that participants with a genetic profile of rs1042778 T-allele and rs2254298 A-allele are affected high versus low emotional warmth, whereas homozygotes of both G-alleles are unaffected by the same environmental influence. Our findings should be, however, interpreted as a null result as the interaction effect did not survive correction for multiple testing.