Summary: Background: Access to gender-affirming medical care has life-saving effects on transgender and gender diverse (TGD) individuals. An increasing number of TGD individuals seek care which led to waiting times of years. We assessed the duration and effects of excessive waiting for gender-affirming care. Methods: In this mixed-methods cross-sectional population study, conducted in the Netherlands between June and August 2019, all TGD individuals with experiences with receiving/applying for gender-affirming medical care could participate. Data of participants waiting for care was primarily analyzed. Demographic characteristics and requested care (multiple-choice questions) and the effects of waiting on health were surveyed (open-ended questions). Descriptive statistics were calculated per treatment, and differences in participant characteristics between those waiting for and already in care were assessed through Chi squared tests and post-hoc testing of residuals. Open text answers were thematically analyzed. Findings: Of all 975 participants, 431 (44.2%) waited for gender-affirming medical care. For 10 out of 20 treatment modalities, the median waiting period was more than a year. Participants already in care were on average higher educated and less-frequently non-binary. Subjective effects of waiting were (very) negative for most treatments. Qualitative findings showed that long waiting was associated with a range of psychosocial distress, poorer health, increasing healthcare consumption, and increased inequality between TGD individuals. Interpretation: Findings confirm that TGD individuals encounter long waiting times in multiple stages of their gender-affirming medical care. Waiting affects both physical and psychosocial health. Individual resilience and resources can mitigate these experiences, which increase inequality within this already marginalized group. Funding: Ministry of Health, Welfare and Sport of the Netherlands and Zorgverzekeraars Nederland (Healthcare Insurers Netherlands).