The purpose of this research was to examine the relationship among clinical carpal tunnel syndrome (CTS) tests and the severity of CTS. A total of 66 subjects with electrodiagnostically confirmed CTS were tested on five CTS tests, then classified according to the severity of CTS. An association was found between testing positive on Phalen's test and the severity of CTS (p < 0.05). In contrast, no association was found between the severity of CTS and results on Tinel's sign, manual version of the carpal compression test (mCCT), Katz-Stirrat hand diagram, or carpal tunnel outcomes assessment tool. The more severe the CTS, the more likely one is to test positive on Phalen's test. Tinel's sign and the mCCT are not influenced by the severity of CTS. This study suggests that Tinel's sign and mCCT may not be useful in assessing the effectiveness of treatment. The Katz-Stirrat hand diagram and the carpal tunnel outcomes assessment tool are not influenced by the severity of CTS, indicating that numerous factors can influence a patient's response on subjective questionnaires.