In this paper, I shall propose a hypothetical interpretation of the phrase tathāgatagarbhaḥ sarvasattvānāṃ, which is a declarative formula of the Mahāparinirvāṇamahāsūtra (abbr. MPMS) and is preserved as original Sanskrit. This phrase confirms that the word tathāgatagarbha—if this is a bahuvrīhi compound—cannot grammatically go with the word sattvānāṃ unlike the case of the Tathāgatagarbhasūtra, in which tathāgatagarbha, being a bahuvrīhi, qualifies the noun sattva (sarvasattvās tathāgatagarbhāḥ). Previous studies have mostly interpreted tathāgatagarbhaḥ of the MPMS, as a tatpuruṣa, whereas I shall keep this as a bahuvrīhi and take it to be an adjective which qualifies some undescribed noun—that is, stūpa, omitted in the phrase, based on the following reasons: (1) The word tathāgatagarbha in the formula is probably premising such expressions like tathāgatadhātugarbhān stūpān, dhātugarbhe caitye (which is paraphrased by the expression sadhātuke caitye “a caitya that contains relics”), etc., as found in other Mahāyāna scriptures, where tathāgatadhātugarbha, as a bahuvrīhi, qualifies the noun stūpa “a stūpa that contains tathāgata's relics”; (2) the omission of the noun stūpa in the formula might reflect the same omission found in expressions, such as dhātudhṛk or dhātudharaḥ (both omitting stūpaḥ), as found in Buddhist inscriptions; (3) The declarative formula of the MPMS should naturally be relevant to the main topic of the MPMS, which deals with tathāgata's nirvāṇa and his relics that were found in stūpas (which, in turn, are reinterpreted in the MPMS from the viewpoint of the dharmakāya and tathāgatagarbha); (4) The MPMS precisely declares that all beings are real stūpa/caitya, and this declaration fits well with the phrase tathāgatagarbhaḥ sarvasattvānāṃ “all beings have tathāgatagarbha (i.e. stūpa)”; (5) We find yet another expression (asmākam upari tathāgatagarbho 'sti “there is tathāgatagarbha above us”) in the Sanskrit fragment of the MPMS; however, the word tathāgatagarbha, in this expression, does not disturb the above- mentioned interpretation. Instead, this reminds us of the famous scene taught in the Saddharmapuṇḍarīka—the stūpa arising in the sky above the audience: saptaratnamayaḥ stūpo ’bhyudgataḥ ... parṣanmaṇḍalasyopari vaihāyasaṃ tiṣṭhet. Accordingly, I shall tentatively propose to interpret the word tathāgatagarbhaḥ in the formula as a bahuvrīhi which qualifies the noun stūpa. I think, however, it is possible to apprehend tathāgatagarbha as a tatpuruṣa, to be the secondary meaning of the word because the MPMS most probably utilizes the word with double or triple meaning in order to preserve the semantic richness of the word garbha, which has already been pointed out by Masahiro Shimoda and Michael Radich.