Because no measure for sexual orientation-related rejection sensitivity (RS) for adolescents exists, we aimed to develop and validate the Sexual Minority Adolescent Rejection Sensitivity Scale (SMA-RSS). In Study 1, interviews with 22 sexual minority youth were conducted (M age = 18.86, SD = 3.03). Based on these interviews, 29 scenarios were developed as potential items for the SMA-RSS. In Study 2, exploratory factor analyses were conducted on these 29 scenarios in a sample of 397 sexual minority adolescents (M age = 16.63, SD = 1.07). The 14 best performing items were selected and a two-factor structure best fit the data. In Study 3, a confirmatory factor analysis was conducted and the test–retest reliability, criterion validity, convergent validity, and incremental validity of the SMA-RSS were assessed in a sample of 499 sexual minority adolescents (M age = 16.61, SD = 1.34). A bifactor model best fit the data and evidence was provided for a strong enough general factor to justify unidimensionality. For criterion validity, the SMA-RSS evidenced small to moderate correlations with minority stressors and mental health indicators. For convergent validity, we found a moderate correlation with general RS. For incremental validity, the SMA-RSS was associated with mental health indicators over and above minority stressors and general RS. Participants were moderately stable in their scores on the SMA-RSS over a one-month period. Taken together, the SMA-RSS captured unique situations in which sexual minority adolescents anxiously expect rejection and can aid in better understanding health disparities among sexual minority adolescents.