Emotion regulation (ER) is the ability to modify arousal and emotional reactivity to achieve goals and maintain adaptive behaviors. ER impairment in autism spectrum disorder (ASD) is thought to underlie many problem behaviors, co-occurring psychiatric symptoms, and social impairment, and yet is largely unaddressed both clinically and in research. There is a critical need to develop ER treatment and assessment options for individuals with ASD across the life span, given the multitude of downstream effects on functioning. This article summarizes the current state of science in ER assessment and treatment and identifies the most promising measurement options and treatments.