Objective: The Covid-19 pandemic has wrought disruption to everyday life and services, and emerging evidence suggests that those with eating disorders (EDs) are likely to experience marked distress and exacerbation of their symptoms. However, little is known around the most relevant factors to symptom change; whether certain emotion regulation and coping strategies are linked to better outcomes; and how people with EDs are adjusting to psychological interventions moving online. Method: In a mixed-method design, we collected qualitative and quantitative data from 207 (76 males) UK residents with self-reported ED, who described and ranked impacts of the pandemic on their symptoms. Regression analysis examined whether emotion regulation strategies were associated with self-reported symptom change, ED symptomatology, and negative emotional states. Thematic analysis explored participants’ experiences of the pandemic, particularly factors affecting their ED, coping strategies used, and experiences of psychological intervention. Results: Most participants (83.1%) reported worsening of ED symptomatology, though factors affecting symptom change differed between specific EDs. Emotion regulation, such as having fewer strategies, poorer emotional clarity, and non-acceptance of emotions, explained nearly half of the variance in emotional distress during the pandemic, and to a lesser extent also predicted ED symptomatology and symptom change. Qualitative findings indicated that difficult emotions (such as fear and uncertainty), changes to routine, confinement and unhelpful social messages were triggering for participants during the pandemic. While some participants described employing positive coping strategies (such as limiting social media exposure), many reported using ED behaviours (among other maladaptive strategies, like alcohol use) to cope with the pandemic. Finally, loss of treatment support, feeling underserving of support and experiencing a ‘detached connection’ online were further exacerbating factors for these participants. Discussion: Our results show that people with EDs have been strongly affected by the pandemic, and that while beneficial for some, online treatment may need some improvement. Our paper discusses implications for online treatment such as taking into account personal circumstances and, in a time where people have limited control over the antecedents of negative emotion, the need to develop skills to manage emotions when they arise.