In China, 173 million adults have a mental disorder, 91.3 per cent of whom have never received professional help. Three factors—knowledge of mental illness, perceptions of the causes of mental illness and the influence of an individual's informal network—were examined to determine their impacts on help-seeking attitudes of Chinese people in Shanghai. A multistage cluster sampling method among six of the twenty districts in Shanghai was adopted. Five hundred and twenty-two participants filled out a questionnaire containing instruments that attempted to measure the three factors. Shanghai Chinese people who had stronger endorsement of psycho-social perspective of mental illness and contemporary treatment methods and weaker endorsement of traditional Chinese beliefs and treatment methods were more inclined to seek professional help. The correct recognition of depression and perceived helpfulness of close friends significantly and inversely predicted help-seeking in depression, whereas the perceived helpfulness of family members was positively related to the tendency to seek help in schizophrenia. This study underlines the need for public education programmes to improve the knowledge of mental illness among Shanghai Chinese people and to equip social workers with skills to assess mental health and engage family members and close friends of the family to help those with mental illness.