To measure the impact of staged implementation of full versus partial ABCDE bundle on mechanical ventilation duration, ICU and hospital lengths of stay, and cost. Prospective cohort study. Two medical ICUs within Montefiore Healthcare Center (Bronx, NY). One thousand eight hundred fifty-five mechanically ventilated patients admitted to ICUs between July 2011 and July 2014. At baseline, spontaneous (B)reathing trials (B) were ongoing in both ICUs; in period 1, (A)wakening and (D)elirium (AD) were implemented in both full and partial bundle ICUs; in period 2, (E)arly mobilization and structured bundle (C)oordination (EC) were implemented in the full bundle (B-AD-EC) but not the partial bundle ICU (B-AD). In the full bundle ICU, 95% patient days were spent in bed before EC (period 1). After EC was implemented (period 2), 65% of patients stood, 54% walked at least once during their ICU stay, and ICU-acquired pressure ulcers and physical restraint use decreased (period 1 vs 2: 39% vs 23% of patients; 30% vs 26% patient days, respectively; p < 0.001 for both). After adjustment for patient-level covariates, implementation of the full (B-AD-EC) versus partial (B-AD) bundle was associated with reduced mechanical ventilation duration (-22.3%; 95% CI, -22.5% to -22.0%; p < 0.001), ICU length of stay (-10.3%; 95% CI, -15.6% to -4.7%; p = 0.028), and hospital length of stay (-7.8%; 95% CI, -8.7% to -6.9%; p = 0.006). Total ICU and hospital cost were also reduced by 24.2% (95% CI, -41.4% to -2.0%; p = 0.03) and 30.2% (95% CI, -46.1% to -9.5%; p = 0.007), respectively. In a clinical practice setting, the addition of (E)arly mobilization and structured (C)oordination of ABCDE bundle components to a spontaneous (B)reathing, (A)wakening, and (D) elirium management background led to substantial reductions in the duration of mechanical ventilation, length of stay, and cost.