This single-center prospective observational study aimed to evaluate sleep architecture in mechanically ventilated pediatric intensive care unit (PICU) patients receiving protocolized light sedation. We enrolled 18 children, 6 months to 17 years of age, receiving mechanical ventilation and standard, protocolized sedation for acute respiratory failure, and monitored them with 24 hours of limited (10 channels) polysomnogram (PSG). The PSG was scored by a sleep technician and reviewed by a pediatric sleep medicine physician. Sixteen children had adequate PSG data for sleep stage scoring. All received continuous opioid infusions, 15 (94%) received dexmedetomidine, and 7 (44%) received intermittent benzodiazepines. Total sleep time was above the age-matched normal reference range (median 867 vs. 641 minutes, p  = 0.002), attributable to increased stage N1 and N2 sleep. Diurnal variation was absent, with a median of 47% of sleep occurring during night-time hours. Rapid eye movement (REM) sleep was observed as absent in most patients ( n  = 12, 75%). Sleep was substantially disrupted, with more awakenings per hour than normal for age (median 2.2 vs. 1.1, p  = 0.008), resulting in a median average sleep period duration (sleep before awakening) of only 25 minutes (interquartile range [IQR]: 14-36) versus normal 72 minutes (IQR: 65-86, p  = 0.001). Higher ketamine and propofol doses were associated with increased sleep disruption. Children receiving targeted, opioid-, and dexmedetomidine-based sedation to facilitate mechanical ventilation for acute respiratory failure have substantial sleep disruption and abnormal sleep architecture, achieving little to no REM sleep. Dexmedetomidine-based sedation does not ensure quality sleep in this population.