The Diagnostic and Statistical Manual of Mental Disorders and International Classification of Diseases classify mental health disorders on the basis of their putatively distinct symptom profiles. Although these nosologies are highly influential, they also have been derided as mere "field guides" because they focus solely on the superficial symptomatic expression of psychiatric syndromes rather than on the commonalities underlying psychiatric disorders. Recently, an alternative transdiagnostic perspective has emerged. This review addresses transdiagnostic processes that underlie a wide range of psychosocial problems commonly addressed by social work practitioners. First, we describe how the transdiagnostic perspective differs from categorical views of psychopathology and accords more closely with scientific evidence. Next, we review current experimental psychopathology and neuroscience research to detail the cognitive, affective, and neurobiological features of five transdiagnostic processes. Finally, we discuss how the transdiagnostic perspective may improve therapeutic outcomes and guide the implementation of targeted social work interventions.