Objective To determine the natural history of the morphology of the median nerve after carpal tunnel decompression. Methods Between October and December 2014, patients with suspected carpal tunnel were prospectively enrolled and underwent pre- and postoperative (3 and 6 months) high-definition ultrasonography, electrophysiology, and clinical testing. Results A total of 81 patients were enrolled in the study; 75 (93%) could be reached for the 6-month follow-up, and 100% were clinically better at the 6-month follow-up. The mean cross-sectional area decreased from 14.3 ± 4.4 mm2 to 9.6 ± 2.3 mm2 (mean ± standard deviation [SD]). The mean distal motor latency decreased from 6.5 ± 2.2 msec to 4.4 ± 0.8 msec (mean ± SD). Distal motor latency improved statistically significantly after surgical decompression as well, but sooner. Conclusion We present the second largest series of patients with sonographic follow-up after surgical decompression of the carpal tunnel.