The COVID-19 pandemic exacerbated socioeconomic disparities in food insecurity. Non-citizens, who do not qualify for most publicly-funded food assistance programs, may be most vulnerable to food insecurity during the pandemic. However, no study has examined heterogeneity in food insecurity by immigration status and ethnicity in the context of the pandemic. We analyzed the 2020 non-restricted California Health Interview Survey to examine disparities in food insecurity by ethnicity and immigration status (i.e., US-born, naturalized, non-citizen) among Asians and Latinxs (N = 19,514) compared to US-born Whites. Weighted multivariable logistic regression analyses assessed the association of immigration status and ethnicity with food insecurity. Decomposition analyses assessed the extent to which pandemic-related economic stressors, including experiencing reduced work hours or losing a job versus pre-pandemic socioeconomic position (SEP), accounted for disparities in food insecurity by ethnicity and immigration status. Regardless of immigration status, Latinxs were more likely to experience food insecurity than Whites. Based on the adjusted analyses, non-citizen, naturalized, and US-born Latinxs had a predicted probability of 12%, 11.4%, and 11.9% of experiencing food insecurity, respectively. In contrast, non-citizen Asians, but not US-born or naturalized Asians, reported greater food insecurity than Whites (12.5% vs. 8.2%). SEP accounted for 43% to 66% of the relationship between immigration status-ethnicity and food insecurity. The pandemic exacerbated economic hardship, but food insecurity was largely explained by long-standing SEP-related factors among Latinxs, regardless of immigration status, and non-citizen Asians. To address disparities in food insecurity, social assistance programs and COVID-19 economic relief should be extended to non-citizens.