Abstract Objectives Although the majority of older people are grandparents, little is known on whether and how the transition into grandparenthood affects their well-being. Moreover, evidence on whether the order of the transition, the time since grandchild’s birth, and the sociodemographic characteristics of the offspring modify the grandparental well-being is scarce. Taking into account these factors, our study examines the association between becoming a grandparent and subsequent well-being. Methods Our study is based on grandparents aged 50 and older from Waves 4–6 of the Survey of Health, Ageing and Retirement in Europe. Using longitudinal analyses, we investigate associations between becoming a grandparent and subsequent life satisfaction, positive affect, and depression controlling for demographic and socioeconomic factors as well as health and well-being at baseline. Furthermore, we explore the role of modifying factors such as whether the grandchild was first-born, the time since transition, and sociodemographic characteristics of the offspring who became a parent. Results Becoming a grandparent has a positive effect on well-being only among women who became grandmothers for the first time and via their daughters. Moreover, this effect is particularly strong in the proximity of the birth of the grandchild. No effects were found among first-time grandfathers. Having an additional grandchild does not affect well-being of grandparents, regardless of the offspring’s characteristics. Discussion Transitioning to grandparenthood per se does not affect well-being. More research is needed to further investigate if interpersonal relationships and changes in roles triggered by becoming a grandparent could help promote well-being in later life.