Emotion dysregulation is a pervasive clinical problem that likely emerges from complex Gene × Environment interactions across development. Epigenetic processes provide a molecular basis by which genotype interacts with the environment across the lifespan to produce phenotype. Epigenetics is defined by molecular processes occurring on and around the genome that regulate gene activity without changing DNA sequence. This chapter describes how epigenetic mechanisms are assessed and provides a brief review of current research on epigenetics, emotion dysregulation, and associated disorders. It then highlights four biological pathways of interest, the serotonin, dopamine, and norepinephrine systems and the limbic-hypothalamic pituitary adrenal (L-HPA) axis, and argues that, to advance understanding of the pathophysiology of emotion dysregulation, biological pathways rather than single genes must be measured. The chapter describes challenges for the field of epigenetics and how novel methods could be leveraged to overcome those challenges.