Individuals with unhealthy alcohol use and comorbid depression or anxiety may be vulnerable to alcohol use escalation in times of stress such as the COVID-19 pandemic. Among a cohort of individuals with pre-pandemic unhealthy drinking, we compared changes in alcohol use by whether people had a depression or anxiety diagnosis, and examined whether mental health treatment was related to these changes. Using electronic health record data from Kaiser Permanente Northern California, we analyzed drinking changes during the pandemic (3/1/2020-6/30/2022) among adults identified in primary care with unhealthy alcohol use (exceeding daily/weekly recommended limits) pre-pandemic (1/1/2019-2/29/2020). Outcomes were mean changes in number of heavy drinking days (prior three months), drinks/week, drinks/day, and drinking days/week. Multivariable linear regression models were fit to: 1) compare outcomes of patients with depression or anxiety diagnoses to those without, and 2) among patients with depression or anxiety, estimate associations between mental health treatment and outcomes. The sample included 62,924 adults with unhealthy alcohol use, of whom 12,281 (19.5%) had depression or anxiety. On average, alcohol use significantly decreased across all measures during the pandemic, but patients with depression or anxiety had greater decreases in drinks/week (adjusted mean difference [aMD] [CI]=-0.34 [-0.55, -0.12]) and drinking days/week (-0.15 [-0.20, -0.10]). No associations were found between mental health treatment and changes in drinking. Contrary to expectations, patients with unhealthy alcohol use and depression or anxiety decreased alcohol use more than those without depression or anxiety during COVID-19, whether or not they accessed mental health services.