During the last years research has shown that Internet-based psychotherapeutic interventions are effective in a number of areas. Based on a cognitive-behavioral treatment protocol for posttraumatic stress disorder (Interapy, Lange et al., 2000), an Internet-based treatment for complicated grief was developed and evaluated and a case study illustrates the treatment procedure. The study evaluated the efficacy of this multiphasic treatment model (self-confrontation, cognitive restructuring, social sharing) on grief-related symptoms, symptoms of general psychopathology and salutary outcome. Further, the online therapeutic alliance as a predictor of salutary treatment outcome was evaluated. Compared with the participants in the waiting control condition, the participants in the experimental group improved significantly on grief-related symptoms and general psychopathology. Overall, treatment effect sizes were large.