This meta-analysis investigates the efficacy of hypnosis in adults undergoing surgical or medical procedures compared to standard care alone or an attention control. Through a comprehensive literature search N=34 eligible randomized controlled trials (RCTs) were included, comprising a total of 2597 patients. Random effects meta-analyses revealed positive treatment effects on emotional distress (g=0.53, CI 95% [0.37; 0.69]), pain (g=0.44, CI 95% [0.26; 0.61]), medication consumption (g=0.38, CI 95% [0.20; 0.56]), physiological parameters (g=0.10, CI 95% [0.02; 0.18]), recovery (g=0.25, CI 95% [0.04; 0.46]), and surgical procedure time (g=0.25, CI 95% [0.12; 0.38]). In conclusion, benefits of hypnosis on various surgically relevant outcomes were demonstrated. However, the internal validity of RCTs seems limited and further high methodological quality RCTs are needed to strengthen the promising evidence of hypnosis for adults undergoing surgery or medical procedures.