We investigated youth's self-reported socio-sexual competences (esteem, assertiveness, control, communication) within their most recent sexual partnerships, and explored disparities in these competences between romantic versus casual sexual partnerships, including age and gender differences therein. Data were used from 6,098 Dutch adolescents and young adults (12.1-26.1 years), who participated in a national study on sexual health. Results indicated that being in love and sexual activity frequency were significant confounders for the associations between sexual partnership typology and youth's socio-sexual competence levels. After controlling for confounding relationship characteristics and sociodemographics, no differences were found between sexual partnership types in youth's sexual esteem, assertiveness, and control. However, romantic sexual partnerships were characterized by more frequent sexual communication than casual sexual partnerships. This pattern was gender-consistent, but for young adults, this difference in sexual communication across sexual partnership types was larger than for adolescents. Our findings emphasize that considering the relationship context (e.g., romantic, casual) for the development, utilization, and evaluation of young people's socio-sexual competencesparticularly sexual communicationis a vital task for parents, educators, clinicians, and researchers. Individual (person-centered) versus relational (dyad-centered) differences in youth's socio-sexual competences require further exploration, as does the link between socio-sexual competences and sexual health and satisfaction.