Importance: It remains uncertain whether invasive ventilation should use low tidal volumes in critically ill patients without acute respiratory distress syndrome (ARDS). Objective: To determine whether a low tidal volume ventilation strategy is more effective than an intermediate tidal volume strategy. Design, Setting, and Participants: A randomized clinical trial, conducted from September 1, 2014, through August 20, 2017, including patients without ARDS expected to not be extubated within 24 hours after start of ventilation from 6 intensive care units in the Netherlands. Interventions: Invasive ventilation using low tidal volumes (n = 477) or intermediate tidal volumes (n = 484). Main Outcomes and Measures: The primary outcome was the number of ventilator-free days and alive at day 28. Secondary outcomes included length of ICU and hospital stay; ICU, hospital, and 28- and 90-day mortality; and development of ARDS, pneumonia, severe atelectasis, or pneumothorax. Results: In total, 961 patients (65% male), with a median age of 68 years (interquartile range [IQR], 59-76), were enrolled. At day 28, 475 patients in the low tidal volume group had a median of 21 ventilator-free days (IQR, 0-26), and 480 patients in the intermediate tidal volume group had a median of 21 ventilator-free days (IQR, 0-26) (mean difference, -0.27 [95% CI, -1.74 to 1.19]; P =.71). There was no significant difference in ICU (median, 6 vs 6 days; 0.39 [-1.09 to 1.89]; P =.58) and hospital (median, 14 vs 15 days; -0.60 [-3.52 to 2.31]; P =.68) length of stay or 28-day (34.9% vs 32.1%; hazard ratio [HR], 1.12 [0.90 to 1.40]; P =.30) and 90-day (39.1% vs 37.8%; HR, 1.07 [0.87 to 1.31]; P =.54) mortality. There was no significant difference in the percentage of patients developing the following adverse events: ARDS (3.8% vs 5.0%; risk ratio [RR], 0.86 [0.59 to 1.24]; P =.38), pneumonia (4.2% vs 3.7%; RR, 1.07 [0.78 to 1.47]; P =.67), severe atelectasis (11.4% vs 11.2%; RR, 1.00 [0.81 to 1.23]; P =.94), and pneumothorax (1.8% vs 1.3%; RR, 1.16 [0.73 to 1.84]; P =.55). Conclusions and Relevance: In patients in the ICU without ARDS who were expected not to be extubated within 24 hours of randomization, a low tidal volume strategy did not result in a greater number of ventilator-free days than an intermediate tidal volume strategy. Trial Registration: ClinicalTrials.gov Identifier: NCT02153294.