Carpal tunnel syndrome is a very common and important disease caused by entrapment of the median nerve in the carpal tunnel. With the widespread use of high-resolution ultrasound, ultrasound is being used usefully in the diagnosis of carpal tunnel syndrome. Compared to electrodiagnostic study, ultrasound examinations are easier and, above all, non-invasive. In addition, ultrasound-guided injection can be performed alone or in combination with ultrasound examination. In the case of nerve hydrodissection, which has recently been spotlighted as a treatment for carpal tunnel syndrome, it is the procedure that could not be attempted before without ultrasound equipment. In this paper, through a comprehensive review of meta-analysis literatures, we look back at the value of ultrasound as a diagnostic tool for carpal tunnel syndrome and the effect of ultrasound-guided injection to get an objective perspective and gain new insights. The usefulness of ultrasound will be largely divided into applications of ultrasound-guided injection, diagnosis, and sonoelastography.