Abstract There is a growing interest in the potential value of qualitative longitudinal research for family sociology. This chapter outlines the value of qualitative longitudinal research (QLR), and particularly its prospective approach, by shedding light on its specific characteristic: the possibility of capturing the evolving temporal dimension of experiences of family transitions, and its subjective character. First, I provide a brief overview of the main features that characterise prospective qualitative research. Second, I illustrate its value for family sociology by providing examples from past and ongoing research studies addressing family transitions. Third, I turn to the challenges that can arise in conducting QLR given its flexibility, the ethical issues that it raises, and the analytical complexities involved in addressing change. I conclude by exploring the underdeveloped opportunities in QLR in family sociology, such as conducting mixed-methods studies and taking advantage of the secondary use of data.