Prolonged grief disorder, characterized by severe, persistent, and disabling grief, has recently been included in the International Classification of Diseases-11 (ICD-11). Emotional disturbances are central to such complicated grief responses. Accordingly, emotion regulation is assumed critical in the development, persistence and treatment of complicated grief. Yet, a comprehensive review on this topic is lacking. We conducted a systematic review (PROSPERO: CRD42017076061) searching PsychInfo, Web of Science and PubMed to identify quantitative research examining relationships between emotion regulation and complicated grief. Sixty-four studies on 7715 bereaved people were identified, focusing on a variety of emotion regulation strategies (i.e., experiential avoidance, behavioral avoidance, expressive suppression, rumination, worry, problem solving, cognitive reappraisal, positive thought, and mindfulness). Our synthesis showed strong evidence that experiential avoidance and rumination play a role in the persistence of complicated grief. More generally, surveys support positive associations between putative maladaptive emotion regulation strategies and complicated grief, and negative associations between putative adaptive emotion regulation strategies and complicated grief. Laboratory research yielded mixed results. Emotion regulation is critical in complicated grief, and in particular experiential avoidance and rumination form important targets in complicated grief treatments. We advise expanding current knowledge, by employing more advanced, intensive data collection methods and experiments across diverse samples. Increasing knowledge in this domain will improve clinical practice.