Abstract Background The data regarding long-term outcomes of early versus delayed invasive strategies in elderly patients who have undergone percutaneous coronary intervention (PCI) for non-ST-segment elevation myocardial infarction (NSTEMI) is limited. Purpose We aimed to investigate the long-term clinical benefit of early versus delayed invasive strategies in elderly patients who underwent PCI for NSTEMI. Methods From a nationwide, prospective, real-world registry of 13,104 patients with acute myocardial infarction (MI) who underwent PCI, 2818 elderly patients (aged ≥70 years) who underwent PCI for NSTEMI were included. Of these, 2299 patients were treated with an early invasive strategy (early invasive group), and 519 were treated later (delayed invasive group). The incidence of major adverse cardiac events (MACE; all-cause death, recurrent MI, any revascularization, stroke, readmission due to heart failure [HF], or definite/probable stent thrombosis [ST]) and the components of MACE were compared using multivariable Cox regression, propensity score (PS) matched, and PS-adjusted analyses. Results During a median follow-up of 1047 days, MACE, all-cause death, and cardiac death occurred in 1018 (36.1%), 660 (23.4%), and 423 patients (15.0%), respectively. The early invasive group showed significantly lower risks of MACE (entire: 35.0% vs. 41.2%, hazard ratio [HR] 0.77, 95% confidence interval [CI] 0.66-0.90, p=0.001; PS-matched: n=984, 33.3% vs. 40.8%, HR 0.75, 95% CI 0.62-0.91, p=0.005), all-cause death (entire: 22.5% vs. 27.4%, HR 0.76, 95% CI 0.63-0.92, p=0.004; PS-matched: 21.8% vs. 27.2%, HR 0.75, 95% CI 0.58-0.90, p=0.005), cardiac death (entire: 13.8% vs. 20.2%, HR 0.64, 95% CI 0.51-0.79, p<0.001; PS-matched: 13.1% vs. 19.4%, HR 0.67, 95% CI 0.55-0.86, p=0.011), and readmission due to HF (entire: 6.5% vs. 9.2%, HR 0.64, 95% CI 0.46-0.89, p=0.007; PS-matched: 6.7% vs. 9.4%, HR 0.68, 95% CI 0.51-0.96, p=0.017) than the delayed invasive group. There were no significant differences in the risks of recurrent MI, any revascularization, stroke, and definite/probable ST between the groups. Furthermore, in patients aged ≥80 years, the early invasive group had significantly reduced rates of MACE (42.9% vs. 49.5%, HR 0.71, 95% CI 0.55-0.91, p=0.039), all-cause death (31.7% vs. 39.0%, HR 0.71, 95% CI 0.55-0.92, p=0.010), and cardiac death (20.9% vs. 31.0%, HR 0.59, 95% CI 0.44-0.80, p=0.001) compared to the delayed invasive group. Conclusions In elderly patients with NSTEMI, an early invasive intervention strategy was associated with favorable long-term clinical outcomes compared to a delayed invasive intervention strategy.