Grief is a prevalent experience in adolescence. Outcomes were explored 6 and 12 months after unguided internet cognitive behavior therapy intervention for grieving adolescents (M = 17.04 years, SD = 1.04). The primary outcome was anxiety symptoms and secondary outcomes were well-beingand symptoms of depression, prolonged grief and posttraumatic stress disorder (PTSD). Of the 49 adolescents randomized at pre-intervention, 18% completed the 6-month follow-up and 27% completed the 12-month follow-up. Intent-to-treat analysis indicated no significant effects of time for the primary outcome of anxiety symptoms, or secondary outcomes of prolonged grief and PTSD symptoms. However, at 12-month follow-up, participants had significantly lower depressive symptoms and higher well-being compared to pre-intervention. Clinical significance analysis showed more participants recovered or improved, compared to those who deteriorated. The study was limited by high attrition, a small sample size and no control group. Future research should include larger samples over long follow-up periods.