The increasing trend in alcohol consumption among women, exacerbated by the COVID-19 pandemic, is of growing concern. Screening, Brief Intervention, and Referral to Treatment in primary care is an efficacious and cost-effective treatment approach for unhealthy alcohol use. However, disparities exist in delivery of brief interventions by sex, age and race/ethnicity. This study measures brief intervention rates among eligible patients by sex, age and race/ethnicity and their intersectionality, in the context of a program of systematic alcohol screening and brief intervention program in adult primary care in a large, integrated healthcare delivery system. Population-based observational study. Primary care clinics in an integrated healthcare delivery system in Northern California, USA. Adult (18+) patients (N=287,551) screening positive for unhealthy alcohol use between January 2014 and December 2017. Receipt of brief intervention, patient and provider characteristics from electronic health records. Multilevel logistic regression showed that women had lower odds of receiving brief intervention than men, across all age, racial/ethnic groups and drinking levels. Sex differences were greater among those aged 35-49 (odds ratio [OR] [95% confidence interval [CI]] = 0.67 [0.64, 0.69]) and 50-65 years (OR [95% CI] = 0.69 [0.66, 0.72]) than among other age groups. Sex differences in odds of receiving brief intervention were greater for the Latino/Hispanic group for women vs. men (OR [95% CI] = 0.69 [0.66, 0.72]) and smaller for the Asian/Pacific Islander group (OR [95% CI] = 0.76 [0.72, 0.81]). In the United States, compared with men, women appear to have lower odds of receiving brief intervention for unhealthy alcohol use across all age groups, particularly during middle age. Black women and Latina/Hispanic women appear to be less likely to receive brief intervention than women in other race/ethnicity groups. Receipt of brief intervention does not appear to differ by drinking levels between men and women.