BackgroundLosing an only child is a particularly traumatic and heartbreaking event for parents, which can trigger a lot of emotional responses, including PTSD and suicidal ideation (SI). The objectives of this study were mainly to identify predictors of SI and examine the interactions of PTSD with stigma and social support on SI among shidu parents.MethodsA total of 507 shidu parents from Shenyang, China were included in this cross-sectional study. Bivariate logistic regression analyses were conducted to explore risk or protective factors associated with SI. Interactions of PTSD with stigma and social support on SI were also examined by bivariate logistic regression analyses.ResultsThe prevalence of SI among shidu parents was 11.24%. PTSD (OR = 2.23, p < 0.05) and stigma (OR = 4.66, p < 0.01) were positively associated with SI. Social support was negatively associated with SI (OR = 0.90, p < 0.01). For individuals with PTSD, the presence of stigma was more likely to lead to SI. For individuals with PTSD, an increased level of social support was less likely to lead to SI.ConclusionsSI is a serious issue among shidu parents. Stigma aggravated the effect of PTSD on SI, while social support buffered the effect of PTSD on SI among shidu parents.