Background Trimetazidine (TMZ) pretreatment protects cardiomyocytes during cardiac surgery. TMZ may protect elderly patients with ischaemic heart disease (IHD) undergoing non-cardiac surgery. Methods This was a randomized, double-blind, placebo-controlled trial (registration #ChiCTR1900025018) of patients with IHD scheduled to undergo non-cardiac surgery at Shenzhen People’s Hospital (Shenzhen, Guangdong Province, China) between June 2014 and September 2015, randomized to 60 mg TMZ or placebo 12 h before surgery. The primary endpoint was the occurrence of in-hospital cardiovascular events. The secondary endpoints were myocardial ischaemia on five-lead electrocardiogram (cECG), cardiac troponin I (cTnI) elevation, cardiac death, acute coronary events, heart failure, and arrhythmia requiring treatments. Results Compared with the placebo group, the TMZ group showed a lower occurrence of in-hospital cardiovascular events (primary endpoint, 20.0% vs. 37.5%, P = 0.02), myocardial ischaemia (15.0% vs. 32.5%, P < 0.01), cTnI elevation (2.5% vs. 10%, P < 0.01), acute coronary events (10.0% vs. 20.0%, P < 0.05), heart failure (0% vs. 2.5%, P < 0.05), and arrhythmia requiring treatment (17.5% vs. 35.0%, P < 0.05). There was no acute myocardial infarction during the 30-day postoperative period. Conclusions In elderly patients with IHD undergoing non-cardiac surgery, TMZ pretreatment was associated with myocardial protective effects. Trial registration The trial was prospectively registered at http://www.chictr.org.cn/showproj.aspx?proj=41909 with registration number [ChiCTR1900025018] (7/8/2019).