Despite recognition that sexual well-being is an important part of adolescent sexual and reproductive health, a clear description of adolescent sexual well-being does not yet exist. Through six in-depth interviews and four focus group discussions with 56 young people in two distinct contexts (Belgium and Ecuador), we used the social-ecological framework to identify factors influencing adolescent sexual well-being. According to respondents, the main factors that influence adolescent sexual well-being are not only situated at the individual (having knowledge and skills and being physically, sexually and mental mature and healthy) and interpersonal levels (positive attraction towards others and communication about sexuality), but at a broader societal level, including social acceptance of sex, gender and sexual diversity and its (legal) translation into comprehensive sexuality education and the ready availability of contraceptives. Our results go well beyond two existing definitions of (adolescent) sexual well-being to contribute to understanding and measurement from the perspective of young people themselves, adding substantively to ongoing discussion about the definition of the concept.