Background/Aims: Endoscopic ultrasound-guided tissue acquisition (EUS-TA) is a standard diagnostic method for biliary tract cancer (BTC), and samples obtained in this manner may be used for comprehensive genomic profiling (CGP). This study evaluated the utility of EUS-TA for CGP in a clinical setting and determined the factors associated with the adequacy of CGP in patients with BTC. Methods: CGP was attempted for 105 samples from 94 patients with BTC at the Aichi Cancer Center, Japan, from October 2019 to April 2022. Results: Overall, 77.1% (81/105) of the samples were adequate for CGP. For 22-G or 19-G fine-needle biopsy (FNB), the sample adequacy was 85.7% (36/42), which was similar to that of surgical specimens (94%, p=0.45). Univariate analysis revealed that 22-G or larger FNB needle usage (86%, p=0.003), the target primary lesions (88%, p=0.015), a target size ≥30 mm (100%, p=0.0013), and number of punctures (90%, p=0.016) were significantly positively associated with CGP sample adequacy. Conclusions: EUS-TA is useful for CGP tissue sampling in patients with BTC. In particular, the use of 22-G or larger FNB needles may allow for specimen adequacy comparable to that of surgical specimens.