Sexual assertiveness is often conceptualized as an individual’s ability to express one’s own sexual needs, desires, and limits. Given that sexual assertiveness is embedded in interactions and can affect not only both partners’ sexual well-being but also relationship satisfaction, dyadic approaches are needed to investigate sexual assertiveness negotiation within adolescent romantic relationships. This qualitative study aimed to document adolescents’ ability to negotiate their sexual needs, desires, and limits with their partners during interactions where they discussed their sexual concerns. A directed content analysis, based on the life positions of the transactional analysis theory, was conducted on the interactions of 40 adolescent romantic dyads aged 14–19 years (M = 16.65; SD = 1.49). The results revealed four categories of strategies: (1) mutual assertiveness: negotiation of one’s own sexual needs, desires, and limits with those of the partner; (2) singular passiveness: repression of one’s own sexual needs, desires, and limits to privilege those of the partner; (3) singular aggressiveness: prioritization of one’s own sexual needs, desires, and limits over those of the partner; and (4) mutual lack of negotiation skills: neglecting both partners’ sexual needs, desires, and limits. Among other things, adolescents’ ability to be sexually assertive was hindered by anticipations, including assumptions leading to disregarding one’s own sexual needs, desires, and limits or fearing to ignore the partner’s. To promote mutually rewarding sexual activities and prevent sexual violence, sexual education initiatives should support adolescents’ ability to assertively negotiate their sexuality with their partner and avoid passiveness, aggressiveness, and lack of negotiation.