The aim of the present study was to contribute to filling the gap by establishing a group psychotherapy for long COVID patients and by evaluating its clinical effectiveness in a single-arm setting. We therefore implemented cognitive-behavioral therapy (CBT) and acceptance and commitment therapy (ACT) elements into group psychotherapy and focused on fatigue, insomnia, depression, anxiety, somatic symptoms, psychotraumatology, and quality of life as psychosomatic outcome measures.