Background:Studies on predictors of outcomes of treatment for common mental health disorders (CMDs) in community mental health settings are scarce, and sample sizes are often small. Research on the impact of identifying as a member of an ethnic minority group on treatment outcomes is limited.Aims:To ascertain whether ethnicity is an independent predictor of outcome and the extent to which any association is mediated by other sociodemographic factors.Method:Retrospective observational study of anonymised treatment data collected for routine clinical purposes. Data were analysed from nine Improving Access to Psychological Therapy (IAPT) services from 2009 to 2016. Social functioning, ethnic group, age, gender, occupation and baseline severity of the mental health disorder were analysed as predictors of outcome.Results:Outcomes varied with ethnic group. Levels of occupation, social deprivation, initial morbidity and social functioning varied between ethnic groups at baseline. After adjustment for these factors the impact of ethnicity was attenuated and only some ethnic groups remained as significant independent predictors of treatment outcome.Conclusions:Ethnic minority status is a marker for multiple disadvantages. Some of the differences in outcome seen between ethnic groups may be the result of more general factors present in all ethnic groups but at greater intensity in some ethnic minority groups.