The purpose of this study was to describe the impact of peer support on post-traumatic stress disorder in parents who have experienced the death of a child, the factors associated with the parents’ post-traumatic stress reactions and the parents’ experiences of peer support. The research data comprise the responses of parents who participated in a family weekend organised by Child Death Families Finland (KAPY). The data were collected 2 weeks before (n = 110) and 2 weeks after (n = 73) the family weekend by a questionnaire consisting of items designed to identify the relevant background variables and the Impact of Event Scale-Revised (IES-R), a self-report measure for assessing post-traumatic stress disorder (PTSD). Statistical methods were applied in the data analysis. No statistically significant differences were observed in the parents’ stress reactions 2 weeks before and 2 weeks after the family weekend. The stress reactions, on the other hand, had a statistically significant association with the self-perceived health of the parents, the age at which their child had died and the time that had elapsed since the death. Two-thirds of the parents regarded the peer support provided during the family weekend as supportive or very supportive. The parents also regarded the support provided during the weekend as important, although the support had no statistically significant impact on their stress reactions. One can draw the conclusion that the parents experienced the family weekend and the peer support provided during it as supportive.