Prolonged grief disorder (PGD) is a new mental health disorder, recently introduced in the International Classification of Diseases (ICD-11), World Health Organization Classification of Diseases (WHO). The new ICD-11 guidelines reflect an emerging wave of interest in the global applicability of mental disorders. However, the selection of diagnostic core features in different cultural contexts has yet to be determined. Currently, there is debate in the field over the global applicability of these guidelines. Using semi-structured interviews with 14 key informants, we explored the acceptability of ICD-11 guidelines for PGD according to Japanese health professionals as key informants. The interviews revealed symptoms of grief possibly missing in the ICD-11 PGD guidelines including somatization and concepts such ashole in the heart. Additionally, sociocultural barriers such as stigma and beliefs about the social desirability of emotions may challenge patients’ and clinicians’ acceptance of the new ICD-11 criteria.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11013-022-09781-6.