Objective To evaluate the application effect of best evidence for sedation assessment in critically ill children on mechanical ventilation and provide a reference for clinical practice. Methods Best evidence for sedation assessment in critically ill children on mechanical ventilation was selected, followed by baseline review and barrier analysis to construct an evidence application strategy. This strategy was implemented in the ICU of a tertiary children′s hospital from August 2023 to January 2024. The study compared ICU nurses′ knowledge mastery of sedation assessment for mechanically ventilated critically ill children, sedation assessment implementation rate, incidence of agitation, duration of mechanical ventilation, ICU length of stay, and rate of unplanned extubation before and after evidence application. Results After the application of evidence, ICU nurses′ scores on knowledge related to sedation assessment of mechanically ventilated critically ill children significantly improved, and the implementation rates of seven audit indicators were significantly higher than baseline levels (all P<0.05). The incidence rate of agitation in patients significantly decreased, and the duration of mechanical ventilation and ICU stay were significantly shortened (all P<0.05). No unplanned extubations occurred in patients before or after evidence application. Conclusion The application of best evidence can improve ICU nurses′ knowledge and sedation assessment implementation rate for mechanically ventilated critically ill children, reduce the incidence rate of agitation, and shorten both mechanical ventilation duration and ICU stay.