Hypersexual behavior is often misunderstood and minimized, and we continue to lack an understanding of what underlies this behavior. Without an understanding of the function of hypersexual behavior, we cannot ascertain the most effective treatment. This study was designed to examine the underlying function of such behavior by exploring whether insecure attachment in men relates to the development of hypersexual behavior. A total of 45 men who were assessed as having Out-of-Control Sexual Behavior (OCSB), utilizing the recently proposed Hypersexual Disorder (HD) diagnosis were compared to 32 men who did not present with OCSB. Participants were directed to an online survey where they completed assessments for hypersexual behavior (The HBI) and attachment style (The ECR-S). Multivariate analysis indicated that high ECR-S scores predicted high HBI scores, high HBI scores tended to show high levels of attachment avoidant behavior and that high ECR-S scores were predictive of the clinical determination of HD. High scores on attachment avoidance, rather than attachment anxiety, were most predictive of the clinical determination of HD. Overall, the avoidant behavior score was a better predictor of OCSB than were attachment anxiety scores. Hypersexual behavior may be a particular manifestation of avoidant attachment and it is this underlying issue that must be addressed to effectively treat HD.