Adjustment disorders are among the most commonly diagnosed mental health disorders in both civilian and military clinical settings. Despite their high prevalence, adjustment disorders have received little research attention. The many gaps in our understanding of this group of disorders hinder the development of adequate, evidence-based treatment protocols. This study utilizes a systematic methodology to identify and prioritize research gaps in adjustment disorders. We used authoritative source reports to identify gaps in research domains from foundational science to services research. Subject-matter experts conducted literature searches to substantiate and refine research gaps, and stakeholders assessed the importance and impact of this work for researchers and policy-makers. We identified 254 possible research-needs statements, which were ultimately reduced to 11 final, prioritized research gaps. Two gaps addressed prevention and screening and three addressed treatment and services research. Six gaps addressed foundational science, epidemiology, and etiology research domains, highlighting the need for basic research. Until some of the basic science questions are resolved (e.g., diagnostic clarity, valid screening, and assessment measures) about adjustment disorders, we may not be able to develop adequate evidence-based interventions for the disorders, and it will be difficult to understand the trajectory of these disorders throughout treatment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).