The optimal timing of intubation was debatable. For a study, researchers sought to investigate the relationship between intubation timing and critically sick individuals’ clinical outcomes. PubMed was systematically searched for studies on the mortality of critically ill patients who underwent early versus delayed intubation. Studies including patients with novel coronavirus illness (COVID-19) were omitted due to the publication of a relevant meta-analysis. Early intubation was determined according to the included studies’ authors. Mortality from all causes was the primary outcome. The pooled risk ratio (RR) and 95% CI were determined using a random effects model. There were 27 trials with 15,441 intubated patients (11,943 early and 3,498 late). Patients having early intubation had a lower all-cause mortality rate than those experiencing late intubation (7,338 fatalities; 45.8% versus 53.5%; RR 0.92, 95% CI 0.87–0.97; P=0.001). This was also observed in the sensitivity analysis of studies defining “early” as intubation within 24 hours of intensive care unit admission (6,279 deaths; 45.8% versus 53.6%; RR 0.93, 95% CI 0.89–0.95; P=0.005). It was possible that a lower fatality rate could be achieved by avoiding late intubation among critically ill patients who do not have COVID-19.