China has an ageing population with the number of older people living alone increasing. Living alone may increase the risk of loneliness of older people, especially for those in China where collectivism and filial piety are emphasised. Social support may fill the need for social contacts, thereby alleviating loneliness. However, little is known about loneliness and social support of older people living alone in China. This study investigated loneliness and social support of older people living alone, by conducting a cross-sectional questionnaire survey with a stratified random cluster sample of 521 community-dwelling older people living alone in a county of Shanghai. Data were collected from November 2011 to March 2012. The instruments used included the UCLA Loneliness Scale version 3 and the Social Support Rate Scale. The participants reported a moderate level of loneliness. Their overall social support level was low compared with the Chinese norm. Children were the major source of objective and subjective support. Of the participants, 53.9% (n = 281) and 47.6% (n = 248) asked for help and confided when they were in trouble, but 84.1% (n = 438) never or rarely attended social activities. The level of loneliness and social support differed among the participants with different sociodemographic characteristics. There were negative correlations between loneliness and overall social support and its three dimensions. The findings suggest that there is a need to provide more social support to older people living alone to decrease their feelings of loneliness. Potential interventions include encouraging more frequent contacts from children, the development of one-to-one 'befriending' and group activity programmes together with identification of vulnerable subgroups.