Past research has shown that attachment orientations shape sexual processes within relationships. Yet, little has been done to explore the opposite direction. In the present research, we examined whether sexual desire and emotional intimacy reduce attachment insecurities over time in emerging relationships. In an 8‐month longitudinal study, we followed 62 newly dating couples across three measurement waves. At Time 1, romantic partners discussed sexual aspects of their relationship and judges coded their displays of sexual desire and intimacy. Participants also completed measures of relationship‐specific attachment anxiety and avoidance in each wave. The results indicated that men's displays of desire predicted a decline in their own and their partner's relationship‐specific insecurities. Conversely, women's displays of desire inhibited the decline in their partner's relationship‐specific insecurities, whereas women's displays of intimacy predicted a decline in their partner's relationship‐specific insecurities. These findings suggest that different sex‐related processes underlie attachment formation in men and women.