Purpose: To assess the rates and variability of do-not-intubate orders in patients with acute respiratory failure. Methods: We conducted a systematic review of observational studies that enrolled adult patients with acute respiratory failure requiring noninvasive ventilation or high-flow nasal cannula oxygen from inception to 2019. Results: Twenty-six studies evaluating 10,755 patients were included. The overall pooled rate of do-not-intubate orders was 27%. The pooled rate of do-not-intubate orders in studies from North America was 14% (range 9–22%), from Europe was 28% (range 13–58%), and from Asia was 38% (range 9–83%), p = 0.001. Do-not-intubate rates were higher in studies with higher patient age and in studies where do-not-intubate decisions were made without reported patient/family input. There were no significant differences in do-not-intubate orders according to illness severity, observed mortality, malignancy comorbidity, or methodological quality. Rates of do-not-intubate orders increased over time from 9% in 2000–2004 to 32% in 2015–2019. Only 12 studies (46%) reported information about do-not-intubate decision-making processes. Only 4 studies (15%) also reported rates of do-not-resuscitate. Conclusions: One in four patients with acute respiratory failure (who receive noninvasive ventilation or high-flow nasal cannula oxygen) has a do-not-intubate order. The rate of do-not-intubate orders has increased over time. There is high inter-study variability in do-not-intubate rates—even when accounting for age and illness severity. There is high variability in patient/family involvement in do-not-intubate decision making processes. Few studies reported differences in rates of do-not-resuscitate and do-not-intubate—even though recovery is very different for acute respiratory failure and cardiac arrest.