Using panel data from the Spanish Labour Force Survey (2008–2016), we explore the risks and opportunities of job transitions (to unemployment, inactivity, full-time work and promotion) of female immigrants and natives in part-time work. This is the first study examining the two possible functions of part-time employment (stepping stone or trap) for different types of women across different working time categories. It contributes to the ongoing discussion about the function of non-standard work by applying an intersectional lens. Our results confirm that the signalling of different types of part-time job works positively, although the signal is weaker for immigrant women, particularly for those working in marginal and substantial part-time employment. The main sociodemographic and structural drivers of labour transitions explain only partially the gross migrant–native differences. As female immigrants experience a stronger outsider position, additional determinants of signalling beyond human capital and labour market segmentation factors might be at work.