The 40-item University of Pennsylvania Smell Identification Test (UPSIT) is the most widely used smell test in the world. Presently, culturally modified versions of this test are available in multiple languages. A traditional Chinese version of the UPSIT (UPSIT-TC) has been developed for administration in Taiwan. The purpose of this study was to investigate the validity and reliability of the UPSIT-TC in Taiwanese patients with chronic rhinosinusitis (CRS). The phenylethyl alcohol (PEA) odor detection threshold test, the North American version of UPSIT (UPSIT-NA), and the UPSIT-TC were administered to 40 healthy subjects and to 100 CRS patients before and after functional endoscopic sinus surgery (FESS). The UPSIT-TC showed good internal consistency (Cronbach's alpha = 0.887, 0.886, and 0.870 at three test occasions) and test-retest reliability (p < 0.001). The scores of UPSIT-TC were significantly correlated to the PEA thresholds (p < 0.001). The UPSIT-TC scores were significantly higher than those of the UPSIT-NA (p = 0.028) when analysis was performed with logistic regression with independent variables including test occasions (before or after FESS), test methods (UPSIT-NA or UPSIT-TC), status of polyp (with or without), and PEA thresholds (improved or did not improve). In addition, there were significant between-group differences in UPSIT-TC scores including healthy versus CRS, CRS with polyps versus CRS without polyps, and PEA thresholds improved versus PEA thresholds which did not improve. The UPSIT-TC is reliable and valid for measuring olfactory function in Taiwanese patients with rhinosinusitis. In addition, the UPSIT-TC clearly resulted in better performance than that of UPSIT-NA.