Background: Parents with intellectual and developmental disabilities (IDDs) are over-represented in child welfare cases. Although IQ "per se" is an invalid indicator of parenting abilities, this study examined the prevalence of judicial consideration of parental IQ test evidence in US appellate cases. Methods: The present authors conducted Boolean searches of Westlaw Corporation's case database since 1999. The present authors used a six-question checklist to survey the 42 most recent American appellate cases involving termination of parental rights (TPR) decisions that included evidence of parental intellectual and developmental disabilities based on IQ. Results: In 86% of cases, parental low IQ was presented as a barrier to parenting competence. Higher courts uphold TPR decision in 81% of cases involving parents with intellectual and developmental disabilities. Conclusions: Parental IQ scores are routinely relied upon to judge parenting capacity in custody cases where parents have intellectual and developmental disabilities. The present authors recommend more comprehensive assessments examining a broader range of contextual variable that may impact on parenting abilities.