Old Uyghur, which is a branch of Old Turkic, was formed on the basis of religious texts of various circles such as Buddhism, Manichaeism and Christianity. Among these, the Buddhist canon has an important place in Old Uyghur translation literature. This paper aims to publish two Old Uyghur fragments belonging to the Faxiang school (法相宗 Faxiang zong), which was developed from the Yogācāra school of Buddhism. Before introducing the paper, it will be useful to present a short overview on the schools of Buddhism. Buddhism, which was founded by Siddhārta Gautama (563-483 bc), who lived in northeastern India, is a philosophical belief system. There are two main schools of Buddhism: Theravāda ‘the way of the elders’ or in other words Hīnayāna ‘small vehicle’, and Mahāyāna ‘great vehicle’. While Hīnayāna constitutes the conservative school of Buddhism, Mahāyāna school is more reformist. Mahāyāna Buddhism has two major philosophical schools within itself: The first is the school of Mādhyamaka, founded by Nāgārjuna and Āryadeva; the second is the Yogācāra school, founded by Asaṅga and Vasubandhu. One of the works of Vasubandhu, who is considered to be one of the founders of the Yogācāra school together with Asaṅga, and whose works left a significant influence on the subsequent Buddhist schools, is Triṃśikā. Vasubandhu’s Triṃśikā and ten prose commentaries on this work led to the emergence of Cheng weishi lun (成唯識論) by Xuanzang (玄奘), who was a Chinese pilgrim, translator and monk. In 629, the author of Cheng weishi lun, Xuanzang’s journey from China to India was influential in introducing Yogācāra Buddhism to China and led to the emergence of the Faxiang school in China. Xuanzang (602-664), who lived in important centers of Buddhist teachings between the years of 629-645, brought to China the Faxiang ‘dharma characteristics’ school, called also Weishi (唯識) ‘consciousnessonly’, as a version of the Yogācāra school in the early Tang Dynasty (618-907). This school was first formed by his disciple Kuiji and other followers based on Cheng weishi lun’s theories of teaching. Important names of the Faxiang school include the first patriarch Kuiji (窺基) (632-682), the second patriarch Hui Zhao (慧沼) (648-714) and the third patriarch Zhi Zhou (智周) (668-723). One of Xuanzang’s disciples, Kuiji, contributed to his teacher’s work, Cheng weishi lun in order to compile commentaries on Triṃśikā in particular. In addition to this, Kuiji wrote a commentary on Cheng weishi lun, called Cheng weishi lun shuji (成唯識 論述記) (Taishō no. 1830, vol. 43, 229a-606c). Two Old Uyghur fragments published in this paper are from a commentary of Xuanzang’s Cheng weishi lun. These fragments belong to chapter 21 of a compilation composed of “at least 30 chapters” (Özertural, 2012, p. 14) containing texts related to the Faxiang school in the Berlin Turfan Collection. Z. Özertural (2012, pp. 207-257, Catalogue no. 248-305), who prepared the catalogue of fragments of the manuscript, states with the reference to the unpublished article entitled “A Preliminary Report on the Study of the so-called Uigur Lehrtext: Chapter 20 and 21” by K. Kitsudō that chapter 21 is a translation into Old Uyghur from a commentary to Xuanzang’s Cheng weishi lun by Queiji. The four Old Uyghur fragments of chapter 21 were previously published by W. Scharlipp in 1986. This paper includes a transcription and transliteration of the fragments in question, translation into Turkish, textual notes, and glossary with an analytical index. The fragments used in the study are Mainz 702 (T I D 7) and Mainz 710 (T I D 6.a). The fragment with archive number Mainz 702 (T I D 7) contains a total of 72 lines, 36 on both sides. However, it is seen that this fragment is destroyed after the 22nd line on recto and the 24th line on verso. In Mainz 710 (T I D 6.a), there are a total of 72 lines, 36 on both sides. Both sides of this fragment are destroyed after the 23rd line. In the textual remarks of his aforementioned article, W. Scharlipp transcribed lines 11-15 on recto of Mainz 702 (T I D 7) and lines 2-13 on verso of the same fragment in order to explain two Buddhist phrases, and he translated these lines into German. In the chapter entitled “Transcription and Transliteration of Old Uyghur text”, we have mainly followed the transcription and transliteration systems used by Röhrborn (cf. 1977-1998, pp. 9-10 and pp. 13-14; 2010, pp. XXXIII-XXXV). In the textual notes, especially the Buddhist terms that existed in the text are mentioned. This paper should be considered as a small contribution to the literature in the understanding of Central Asian Turkish Buddhism.