Prolonged Grief Disorder (PGD) is included in ICD-11 and DSM-5-TR and includes a requirement of cultural deviance. This study examined endorsement rates and factors associated with endorsement of this criterion among Danish bereaved spouses (n = 425) and their adult children (n = 159) four years post-loss. In total, 7.5% (n = 44) participants endorsed this criterion. Both including and excluding the criterion, the prevalence rates for probable DSM-5-TR PGD were 1.4% (n = 8) and 1.7% (n = 10), respectively and for probable ICD-11 PGD were 1.4% (n = 8) and 2.2% (n = 13), respectively. Age and gender of the deceased, age of the bereaved, greater grief severity, and comorbid psychopathology were positively associated with endorsement of the criterion. Findings demonstrate low endorsement of the cultural deviation criterion, that its inclusion excludes several potential PGD cases, and unanticipated associations with several factors raise questions about the criterion's validity.