Foreign domestic helpers constitute a significant proportion of migrant workers worldwide. This population subgroup provides an opportunity for understanding social determinants of oral health in immigrant community. A random sample of 122 Indonesian domestic helpers in Hong Kong completed a questionnaire on their demographic background, social characteristics (competency in local languages, immigration history, living condition, social connections, and leisure activities) and oral health behaviours (knowledge, attitudes, practice and self-efficacy). Their tooth status and periodontal health were assessed. Participants tended to start flossing after settling in Hong Kong. Favourable oral health knowledge was found in more acculturated participants, as indicated by proficiency in local languages and immigration history. Engagement in social and/or religious activities and decent living condition provided by employers were associated with favourable oral health behaviours and/or better oral health. Social determinants explained 13.2 % of variance in caries severity. Our findings support the significant impact of social circumstances on oral health of domestic workers.