Objectives Polycystic Ovary Syndrome (PCOS) is a common female endocrine disorder presenting as early as adolescence. Recent data suggest that Asians may be at increased risk. This study examines PCOS prevalence by race/ethnicity in a large, diverse population of adolescent females. Methods This retrospective study included 244,642 females (ages 13–17) with well-child visits during 2012–2018 in a Northern California healthcare system. Race/ethnicity and Asian ethnicity were classified using self-reported data. Body mass index was classified as healthy, overweight, and moderate/severe obesity. PCOS was determined by clinical diagnosis within one year of the visit. Results The overall prevalence of PCOS was 0.7% and increased substantially with weight. Among those with obesity, PCOS prevalence was 4.2, 2.9, 2.4, 2.1% in Asian/Pacific Islander (PI), Hispanic/Latina, Non-Hispanic White, Black adolescents and 7.8, 6.7, 5.7, 3.4% in South Asian, Chinese, Filipina, Native Hawaiian/PI adolescents, respectively. Compared to White adolescents, Asian/PIs had two-fold higher risk of PCOS, and Hispanic/Latinas had 1.3-fold higher risk. Compared to Chinese adolescents, South Asians had 1.7-fold higher risk, while Native Hawaiian/PIs had half the risk. Conclusions The increased burden of diagnosed PCOS in Asian/PI and Hispanic/Latina adolescents, especially those with obesity, calls for further examination and clinical surveillance of at-risk populations.