Objective To investigate whether remote ischaemic preconditioning (RIPC) prevents myocardial injury in patients undergoing hip fracture surgery. Design Phase II, multicentre, randomised, observer blinded, clinical trial. Setting Three Danish university hospitals, 2015-17. Participants 648 patients with cardiovascular risk factors undergoing hip fracture surgery. 286 patients were assigned to RIPC and 287 were assigned to standard practice (control group). Intervention The RIPC procedure was initiated before surgery with a tourniquet applied to the upper arm and consisted of four cycles of forearm ischaemia for five minutes followed by reperfusion for five minutes. Main outcome measures The original primary outcome was myocardial injury within four days of surgery, defined as a peak plasma cardiac troponin I concentration of 45 ng/L or more caused by ischaemia. The revised primary outcome was myocardial injury within four days of surgery, defined as a peak plasma cardiac troponin I concentration of 45 ng/L or more or high sensitive troponin I greater than 24 ng/L (the primary outcome was changed owing to availability of testing). Secondary outcomes were peak plasma troponin I and total troponin I release during the first four days after surgery (cardiac and high sensitive troponin I), perioperative myocardial infarction, major adverse cardiovascular events, and all cause mortality within 30 days of surgery, length of postoperative stay, and length of stay in the intensive care unit. Several planned secondary outcomes will be reported elsewhere. Results 573 of the 648 randomised patients were included in the intention-to-treat analysis (mean age 79 (SD 10) years; 399 (70%) women). The primary outcome occurred in 25 of 168 (15%) patients in the RIPC group and 45 of 158 (28%) in the control group (odds ratio 0.44, 95% confidence interval 0.25 to 0.76; P=0.003). The revised primary outcome occurred in 57 of 286 patients (20%) in the RIPC group and 90 of 287 (31%) in the control group (0.55, 0.37 to 0.80; P=0.002). Myocardial infarction occurred in 10 patients (3%) in the RIPC group and 21 patients (7%) in the control group (0.46, 0.21 to 0.99; P=0.04). Statistical power was insufficient to draw firm conclusions on differences between groups for the other clinical secondary outcomes (major adverse cardiovascular events, 30 day all cause mortality, length of postoperative stay, and length of stay in the intensive care unit). Conclusions RIPC reduced the risk of myocardial injury and infarction after emergency hip fracture surgery. It cannot be concluded that RIPC overall prevents major adverse cardiovascular events after surgery. The findings support larger scale clinical trials to assess longer term clinical outcomes and mortality. Trial registration ClinicalTrials.gov NCT02344797.