Parents Anonymous(R) is a mutual support self-help group aimed at strengthening families and reducing child maltreatment. The purpose of the study was to assess whether parents' participation in Parents Anonymous(R) was associated with child maltreatment outcomes and with their change in risk and protective factors. In the quantitative segment of the evaluation, 206 parents new to Parents Anonymous(R) were interviewed at three times. Change in study measures was assessed in the short term (one month) and in the long term (six months). In the qualitative segment, 36 parents from Spanish-language Parents Anonymous(R) groups in two states were assessed with semi-structured, in-person interviews. Additional qualitative data was collected through group observations and focus groups.