The aim of this systematic review was to estimate the efficiency of hypnosis prior to medical procedures. Different databases were analyzed to identify randomized controlled trials (RCTs) comparing hypnosis to control interventions. All RCTs had to report pain or anxiety. Eighteen RCTs with a total of 968 patients were included; study size was from 20 to 200 patients (14 RCTs ≤ 60 patients). Fourteen RCTs included 830 adults and 4 RCTs included 138 children. Twelve of 18 RCTs had major quality limitations related to unclear allocation concealments, provider's experience in hypnosis, patient's adherence to hypnotic procedures, and intention-to-treat design. This systematic review observed major methodological limitations in RCTs on hypnosis prior to medical procedures.