Background: Lone parents in high-income countries have high rates of poverty (including in-work poverty) and poor health. Employment requirements for these parents are increasingly common. 'Welfare-to-work' (WtW) interventions involving financial sanctions and incentives, training, childcare subsidies and lifetime limits on benefit receipt have been used to support or mandate employment among lone parents. These and other interventions that affect employment and income may also affect people's health, and it is important to understand the available evidence on these effects in lone parents. Objectives: To assess the effects of WtW interventions on mental and physical health in lone parents and their children living in high-income countries. The secondary objective is to assess the effects of welfare-to-work interventions on employment and income.