The objective of this study was to evaluate the responsiveness and construct validity of the Spanish version of the DASH as outcome measure for carpal tunnel surgery. The study population was 42 patients with the diagnosis of carpal tunnel syndrome (CTS) based on clinical and electrophysiological criteria. The clinical design was a classic Cohort study with measures the day before and 12 weeks after open carpal tunnel release. The Spanish version of the DASH was compared to the physical exam measures as dexterity time, grip and pinch strength, range of motion of the wrist (ROM) and two-point discrimination (2PPD). The responsiveness was evaluated based on the effect size (ES) and the standardised response means (SRM). The Spanish version of the CTS questionnaire (CTQ) and the Spanish version of the 36-item short-form health survey (SF-36) were self-administered to the same study population and followed the same clinical design. The hypothesis that the DASH instrument should present a responsiveness level higher than the SF-36 and lower than the CTQ was established to demonstrate the construct validity. The DASH instrument showed an ES of 0.68 and an SRM of 1.00. Responsiveness of traditional physical exam measures were lower, running from 0.35 (SRM) for dexterity time to 0.00 (ES) for key pinch strength. The SF-36 presented a responsiveness level (range from 0.07 to 0.14) lower that the DASH. The CTQ showed the highest level of responsiveness (ES = 1.41 and 0.7) (SRM = 1.75 and 0.51). In conclusion, The DASH instrument is more sensitive in detecting clinical change than the physical exam measures for use in clinical outcome studies of CTS done at 12 weeks after surgery. The Spanish DASH showed a responsiveness lower than the CTQ and higher than the SF-36 as a proof of a good construct validity.