Objectives The aim of this study was to compare a delayed and a very early invasive strategy in patients with non–ST-segment elevation acute coronary syndromes (NSTE-ACS) without pre-treatment. Background The optimal delay of the invasive strategy in patients with NSTE-ACS remains debated and has never been investigated in patients not pre-treated with P2Y12–adenosine diphosphate receptor antagonists. Methods A prospective, open-label, randomized controlled trial was conducted. Altogether, 741 patients presenting with intermediate- or high-risk NSTE-ACS intended for an invasive strategy were included. The modified intention-to-treat analysis was composed of 709 patients after 32 withdrew consent. Patients were randomized 1:1 to the delayed invasive group (DG) (n = 363) with coronary angiography (CA) performed 12 to 72 h after randomization or the very early invasive group (EG) (n = 346) with CA within 2 h. No pre-treatment with a loading dose of a P2Y12–adenosine diphosphate receptor antagonist was allowed before CA. The primary endpoint was the composite of cardiovascular death and recurrent ischemic events at 1 month, as determined by a blinded adjudication committee. Results Most patients had high-risk NSTE-ACS in both groups (93% in the EG vs. 92.5% in the DG). The median time between randomization and CA was 0 h (interquartile range [IQR]: 0 to 1 h) in the EG group and 18 h (IQR: 11 to 23 h) in the DG. The primary endpoint rate was significantly lower in the EG (4.4% vs. 21.3% in the DG; hazard ratio: 0.20; 95% confidence interval: 0.11 to 0.34; p < 0.001), driven by a reduction in recurrent ischemic events (19.8% vs. 2.9%; p < 0.001). No difference was observed for cardiovascular death. Conclusions Without pre-treatment, a very early invasive strategy was associated with a significant reduction in ischemic events at the time of percutaneous coronary intervention in patients with intermediate- and high-risk NSTE-ACS. (Early or Delayed Revascularization for Intermediate and High-Risk Non ST-Elevation Acute Coronary Syndromes; NCT02750579)