This article provides new evidence on the relationship between benefit conditionality and mental health. Using data on Temporary Assistance for Needy Families policies (TANF) – the main form of poverty relief in the United States – it explores whether the mental health of low-educated single mothers varies according to the stringency of conditionality requirements attached to receipt of benefit. Specifically, the article combines state-level data on sanctioning practices, work requirements and welfare-to-work spending with health data from the Behavioral Risk Factor Surveillance System and evaluates the impact of conditionality on mental health over a fifteen-year period (2000 to 2015). It finds that states that have harsher sanctions, stricter job search requirements and higher expenditure on welfare-to-work policies, have worse mental health among low-educated single mothers. There is also evidence that between-wave increases in the stringency of conditionality requirements are associated with deteriorations in mental health among the recipient population. It is suggested that these findings may reflect an overall effect of ‘intensive conditionality’, rather than of the individual variables per se. The article ends by considering the wider implications for policy and research.