Maladaptive daydreaming (MD) is a dysfunctional coping mechanism that involves excessive, uncontrollable daydreaming. MD accounts for severe impairment in life functioning and is comorbid with several psychopathological disorders, sharing common maladaptive features such as compulsion and emotional dysregulation. We conducted a scoping review of the research on MD. We aimed to clarify the definition of MD, its underlying psychological mechanisms, and characteristics of the published research. We searched MEDLINE, PsycINFO, SCOPUS, Web of Science Core Collection, and secondary sources for MD-focused empirical studies published in English until March 2024. Two independent screeners performed abstract and full-text screening and data extraction. This review included 89 studies, of which 87 were published and two were unpublished studies. MD research showed an increasing trend of studies since 2002 with geographical diversity. Most studies presented online cross-sectional data with younger female participants and explored prevalence, associated psychological correlates, and comorbidity with mental disorders. A total of 66 studies were conducted in the general population, MDers, and student samples. Among clinical studies (n = 23), eight focused on specific diagnoses, seven included mixed clinical groups, and eight were case studies. Our review innovately reported the diverse methodologies used in MD research, especially involving clinical populations, and suggests future studies focus on heterogeneous samples, namely, in diverse clinical groups to explore differences in MD levels across these groups, longitudinal study designs, and the effectiveness of treatment strategies that will aid policymaking and the creation of valid resources for mental health professionals to diminish the negative impact of MD.