Background: Early mobilization benefits critically ill patients. Scant information is available about adherence to early mobilization protocols in intensive care units (ICU). With the aim of optimizing the application of our early mobilization protocol in mechanically ventilated patients in routine daily practice, this study analyzed adherence to the protocol, impediments to adherence, and adverse eventsin our ICU. Methods: This observational study analyzed data collected prospectively at a 24-bed polyvalent ICU over a three-year period (2017–2019). Data from adult patients on mechanical ventilation > 48 hours who met the inclusion criteria for the early mobilization protocol were included. We analyzed demographics, adherence to the protocol, total number of mobilizations, impediments to early mobilization, artificial airway/ventilatory support at each mobilization level, and adverse events during mobilization. All data was automatically obtained from the clinical information system by extract, transform, and load processes using Python 3.0. The unit of analysis was ICU stay-day. Results: We analyzed 3269 stay-days from 388 patients with median age of 63 (51–72) years, median APACHE II 23 (18–29) and median ICU stay of 10.1 (6.2–16.5) days. Adherence to the protocol was 56.6% (1850 stay-days), but patients were mobilized in only 32.2% (1472) of all stay-days. The most common reasons for not mobilizing patients were failure to meeting the criteria for clinical stability in 241 (42%) stay-days and unavailability of physiotherapists in 190 (33%) stay-days. Adverse events occurred in only 6 (0.4%) stay-days mobilizations. Conclusions: Although adherence to the protocol was high, patients were mobilized in only one-third of all stay-days. This study points to ways we can improve early mobilization in our ICU, including assessing the suitability of the criteria for clinical stability and increasing the presence of physiotherapists.