<p>Research on adolescents and young adults living with perinatally acquired Human Immunodeficiency Virus (HIV) has largely emphasized biomedical aspects, with limited attention to developmental and psychosocial dimensions. This study explored how Portuguese adolescents and young adults understand their diagnosis, adapt to living with HIV, and perceive its impact across life domains. Twelve semi-structured interviews with youth receiving care at a pediatric hospital in northern Portugal were analyzed using Thematic Analysis. Findings highlighted a continuum of adaptation, ranging from denial and resistance to gradual acceptance and integration of the condition into daily life. Adaptation trajectories were shaped by the timing and manner of diagnosis disclosure, treatment adherence, stigma, and the presence or absence of supportive relationships. Secrecy emerged as a predominant strategy to manage anticipated stigma, particularly in family, school, and healthcare contexts, but often reinforced isolation. Challenges were especially acute in intimate relationships and future planning, where disclosure dilemmas intensified fears of rejection. The study underscores the need for developmentally sensitive, stigma-informed, and family-engaged interventions to support disclosure processes, strengthen adherence, and promote psychosocial well-being. Addressing these issues is crucial to fostering resilience and inclusion among young people living with perinatally acquired HIV.</p>