The global shortage of skilled anaesthesiologists, surgeons and obstetricians is a leading cause of high unmet surgical need. Although anaesthetic and surgical task-shifting are widely practiced to mitigate this barrier, little is known about their safety and efficacy. This systematic review seeks to highlight the existing evidence on the clinical outcomes of patients operated on by non-physicians or non-specialist physicians globally. Relevant articles were identified by searching four databases (MEDLINE, Embase, CINAHL, and Global Health) in all languages between 2008 and February 2022. Retrieved documents were screened against pre-specified inclusion and exclusion criteria and their qualities were appraised critically. Data were extracted by two independent reviewers and findings were synthesised narratively. In total, 40 studies have been included. Thirty-five focus on task-shifting for surgical and obstetric procedures, whereas four studies address anaesthetic task-shifting; one study covers both interventions. The majority are located in Sub-Saharan Africa and the United States. Seventy-five percent present perioperative mortality outcomes and 85% analyse morbidity measures. Evidence from low- and middle-income countries, which primarily concentrates on caesarean sections, hernia repairs, and surgical male circumcisions, points to the overall safety of non-surgeons. On the other hand, the literature on surgical task-shifting in high-income countries is limited to nine studies analysing tube thoracostomies, neurosurgical procedures, caesarean sections, male circumcisions, and basal cell carcinoma excisions. Finally, only five studies pertaining to anaesthetic task-shifting across all country settings answer the research question with conflicting results, making it difficult to draw conclusions on the quality of non-physician anaesthetic care. Overall, it appears that non-specialists can safely perform high-volume, low-complexity operations. Further research is needed to understand the implications of surgical task-shifting in high-income countries and to better assess the performance of non-specialist anaesthesia providers. Future studies must adopt randomised study designs and include long-term outcome measures to generate high quality evidence.