Comprised of eight discrete disorders, the DSM-5-TR category of depressive disorders is a hallmark of mental health assessment and treatment for practitioners who intersect with the field of mental health. Depressive disorders are common across age groups and diverse populations and costly to the individual, clinicians, families, and societies touched by them. As such, accurate assessment and diagnosis is a critical step in providing support and care for those with depressive symptoms. This chapter aims to provide an outline of evidence-based assessment and diagnostic considerations for depressive disorders. First, an overview of the diagnostic criteria for each depressive disorder defined within the DSM-5-TR is provided. Then, the common procedures, methods, and instruments for screening, assessing, and diagnosing depressive disorders across the lifespan are presented to equip practitioners with evidence-based methods for gathering information on depressive disorders. Finally, important cultural, social, individual, and medical considerations are included for accurate and differential diagnosis. Throughout the chapter, case examples and current best practices are introduced to create context for how the complexities of depressive disorders may present themselves in primary care, mental health, and other social service settings.