This article explores the impact of losing a child, especially losing all children (including losing the only child), on the mental health, happiness and loneliness of parents. The Chinese government has implemented strict restrictions on the number of births for each family since the 1970s, resulting in the creation of millions of only-child families. Using the 2011 baseline data from the China Health and Retirement Longitudinal Study, we find that the bereavement of a child is associated with lower levels of mental health and happiness and higher levels of loneliness for the parents, even after we adjust for demographic and socioeconomic characteristics. The effects are significantly stronger for losing all the children. Results have strong implications for the population-control, elderly-care and mental-care policies especially in China and developing countries, where the social security system is not yet sound.