Background: The diagnosis of the rare genetic diseases has great importance in treating multisystemic conditions, preventing potential complications, and estimating disease risk for family members. The duration of obtaining genetic test results is varies. The demand to learn the diagnosis of a possible untreatable illness involves a struggle between uncertainty and a lifetime chronic disease. The current uncertainty of their child's condition and the long wait for a diagnosis may increase the parents' anxiety level and cause difficulties in the continuation of diagnostic procedures in some families. This study aimed to investigate the prediagnosis and postdiagnosis anxiety levels of parents who have a child with a rare genetic disease.