There is growing concern about the problem of in-work poverty in the UK. Despite this, the literature on in-work poverty remains small in comparison with that on low pay and, in particular, we know relatively little about how people move in and out of in-work poverty. This paper presents an analysis of in-work poverty transitions in the UK, and extends the literature in this field in a number of identified ways. The paper finds that in-work poverty is more transitory than poverty amongst working-age adults more generally, and that the number of workers in the household is a particularly strong predictor of in-work poverty transitions. For most, in-work poverty is a temporary phenomenon, and most exits are by exiting poverty while remaining in work. However, our study finds that respondents who experience in-work poverty are three times more likely than non-poor workers to become workless, while one-quarter of respondents in workless, poor families who gained work entered in-work poverty. These findings demonstrate the limits to which work provides a route out of poverty, and points to the importance of trying to support positive transitions while minimising negative shocks faced by working poor families.