Given the rise of digital technology and its assumed impact on psychological well-being, this scoping review systematically examines the literature on Fear of Missing Out (FoMO), which is assumed to play a pivotal role in this dynamic. Although adverse effects of FoMO are commonly assumed, there is still no consensus on the nature of the phenomenon or its relations with psychological well-being and digital technology use, making a scoping review essential. To address this need, we comprehensively assess the conceptualizations of the construct of FoMO and its roles in relation to well-being and digital technology use. We conducted a literature search in PubMed, Ebsco/APA PsycINFO, and Web of Science (period 2013 to July 7, 2023), screening 4121 articles at the title and abstract level and assessing 342 full-text articles for eligibility, ultimately including 106 articles. The review revealed a fragmented FoMO literature, emphasizing the need for conceptual clarity to address critical gaps and inconsistencies in existing research. Consensus exists on FoMO’s essence—an unpleasant feeling arising from missed social experiences driven by activity comparison. However, debates include FoMO’s associated affective states and conceptual boundaries, as well as the need to disentangle FoMO as a trait or state. The review also underscored FoMO’s multifaceted roles in well-being and digital technology use, highlighting the need for causal research, theoretical guidance, and unified terminology to advance understanding in the FoMO literature.