The aim was to study mothers' experiences of online peer support groups after the death of a child. Participants (N = 8) were recruited through a newsletter for the Swedish association for families/children with heart defects, and two closed support groups on Facebook (900 and 100 members) and interviewed by telephone. Transcripts were analyzed with qualitative content analysis. The groups were available around the clock, regardless of support need, and mothers joined both to receive and provide support. Participation in online peer support groups may provide a sense of belonging to a caring community and serve as a valuable complement to healthcare.