Current, otherwise efficacious, psychosocial interventions fail to adequately treat a large subgroup of patients experiencing distress (e.g., distress disorders, contextual distress), potentially due to core transdiagnostic factors like excessive emotionality and perseverative negative thought (PNT). An affective science and functional emotion regulation perspective offers a framework for honing interventions to more precisely target these factors and improve treatment for distress-related conditions. Aligned with such a framework, this chapter introduces emotion regulation therapy (ERT). Specifically, ERT draws together therapeutic processes from across the intervention spectrum to target the emotional/motivational, dysregulatory (i.e., PNT), and behavioural mechanisms that are hypothesized to maintain distress. Two sequential treatment phases and the clinical interventions that comprise each phase are described, followed by a discussion of conceptualization and idiographic adaptation in ERT. The chapter concludes with a demonstrative case study to exemplify treatment progression.