Carpal tunnel syndrome is a condition where one of two main nerves in the wrist is compressed, which can lead to pain in the hand, wrist and sometimes forearm, and numbness and tingling in the thumb, index and long finger. In advanced cases some of the muscles of the hand can become weak. Carpal tunnel syndrome is more common in women and older age groups. Many people undergo surgery to treat this condition, though sometimes other treatments, such as therapeutic ultrasound, are offered. Therapeutic ultrasound involves applying a round-headed instrument to the skin of the painful area, to deliver sound waves that are absorbed by the underlying tissues, to help relieve pain and lessen disability. We searched for study reports and found 11 randomised controlled trials including 443 participants overall that assessed the safety and benefit of therapeutic ultrasound for people with carpal tunnel syndrome. The risk of bias of studies was low in some studies and unclear or high in others. There is only poor quality evidence from very limited data to suggest that therapeutic ultrasound may be more effective than placebo for either short- or long-term symptom improvement in people with carpal tunnel syndrome. There is insufficient evidence to support the greater benefit of one type of therapeutic ultrasound regimen over another or to support the use of therapeutic ultrasound as a treatment with greater efficacy compared with other non-surgical interventions for carpal tunnel syndrome, such as splinting, exercises, and oral drugs. Few studies measured adverse effects to therapeutic ultrasound. More research is needed to find out how effective and safe therapeutic ultrasound is for people with carpal tunnel syndrome, particularly in the long term.