Purpose <p>Research on the experiences of autistic adults in China is extremely limited. This study explored the diagnostic experiences of young autistic adults from the Chinese mainland, focusing on barriers to timely diagnosis and post-diagnostic reactions within China’s sociocultural context.</p> Method <p>Eighteen autistic adults (9 males, 9 females) aged 20–30 years completed semi-structured interviews consisting of open-ended questions regarding their diagnostic experiences. Interview data were analyzed using thematic analysis.</p> Results <p>Three major themes were generated from the interview data: (1) barriers to recognizing autism; (2) navigating a challenging path to diagnosis; and (3) reconstructing self and relationships after diagnosis. Participants encountered diagnostic barriers across familial, educational, cultural, and systemic domains. Post-diagnosis, many participants experienced relief and enhanced self-understanding, though reactions from parents varied, and workplace disclosure posed challenges.</p> Conclusion <p>This study provides valuable insights into the diagnostic challenges and post-diagnosis experiences of Chinese autistic adults. The findings underscore the need for improved diagnostic services and greater public awareness of autism in the Chinese mainland.</p>