Contrary to conventional wisdom, recent studies argue that parenthood is not necessarily related to higher parental subjective well-being (SWB). However, parenthood remains an important aspect of adults' lives, also in highly developed societies where childbearing has become optional, financially expensive and affecting other goals in life. Whereas a great deal of effort has been put into answering why fertility is low in so many developed countries, one may even ask why is it not even lower. The answer is not obvious but stems from the fact that, to date, the relationship between fertility and SWB has been understudied and the mechanisms at work are not well understood. This special issue makes a step forward in this line of research, providing a coherent set of papers addressing different dimensions of the relationship between fertility and SWB and its mechanisms, starting from a demographic perspective, but integrating theories and research results from other disciplines. The collection of papers assesses the effect of the birth of a child on the individual SWB from angles still unexplored with the idea that the effects of fertility on individuals' SWB are diverse depending on individual, couple and country contextual factors.