It has been suggested that self-monitoring (the propensity to exercise self-control on one’s expressive behavior and self-presentation guided by situational cues) and sociosexual orientation (the degree of preferring short-term association in sexual relationships) are associated with each other. Using four groups of Japanese participants (heterosexual and non-heterosexual men and women), we demonstrated that there was a robust association within each of the groups. The association of self-monitoring with sociosexuality was considerably stronger and more stable than that of other putative factors such as family stress in the early stages of life or the level of self-esteem. The possible effect of prenatal androgen levels on self-monitoring and sociosexuality was investigated using the masculinity of preferred play in childhood as an alternative measure; however, no significant correlation was observed. These results suggested that common substrates between self-monitoring and sociosexuality exist, irrespective of population differences. However, the difference in the prenatal androgen levels to which the participants had been exposed was an unlikely candidate.