BACKGROUND: Major depression is increasing world-wide, and is the fourth leading cause of the global disease burden. Depression is rarely diagnosed in primary care settings in Vietnam, and those afflicted usually only seek professional care when the illness has become very severe. Depressive disorders affecting mothers are an important cause of low birth-weight, childhood stunting, under nutrition and adverse mental development, and a study has shown a 33% prevalence of postnatal depression symptoms in Ho Chi Minh City. METHODS: The aim of this study was to elicit Illness Explanatory Models (EMs) of depression and postnatal depression from nine mothers and nine health workers. The study was conducted in a semi-rural area in Vietnam, and the EMs were elicited through semi-structured interviews where a case vignette of depression was used as the basis of questioning. RESULTS: The EMs elicited were predominantly somatosocial in nature and the mothers assigned a strong personal responsibility for care. Psychiatric treatment and care was seldom recommended. Lack of communication was described as an important factor concealing depression, and together with the lack of care-seeking can be expected to impede effective treatment. LIMITATIONS: The results of this study cannot be generalised beyond the group studied, or the context of Ba Vi, though we believe that analytical generalisation to other contexts can be made. CONCLUSION (CLINICAL RELEVANCE): The results of this study highlight the importance of depression and postnatal depression being diagnosed in primary care, and of a cross-sectoral approach for the prevention of depression in Vietnam, which takes into account the social causation of depression in women.