Background: Bacterial infections (BIs) are widespread in ICU. The aims of this study were to assess the compliance with antibiotic recommendations, and factors associated with non-compliance. Methods: We conducted an observational study in eight French Pediatric and Neonatal ICUs with an antimicrobial stewardship program mostly once a week. All children receiving antibiotics for a suspected or proven BI were evaluated. Newborns Results: 139 suspected (or proven) BI episodes in 134 children were prospectively included during six separate time-periods over one year. The final diagnosis was 26.6% no bacterial infection, 40.3% presumed bacterial infection, and 35.3% documented bacterial infection. Non-compliance for all parameters occurred in 51.1%, with errors mainly concerning the antimicrobials’ choice (27.3%), duration of each antimicrobial (26.3%), and duration of antibiotic therapy (18.0%). In multivariate analysis, main independent risk factors of non-compliance were prescribing ≥2 antibiotics (OR 4.06, 95% CI 1.69-9.74, p=0.0017), a duration of broad-spectrum antibiotic therapy ≥4 days (OR 2.59, 95% CI 1.16-5.78, p=0.0199), suspecting catheter-related bacteremia (ORs 3.70 and 5.42, 95% CIs 1.32 to 15.07, pConclusions: Half of antibiotic prescriptions remain non-compliant with guidelines. Intensivists should daily reassess the benefit of using several or broad-spectrum antimicrobials and stop antibiotics that are no longer indicated. Developing consensus about treating specific illnesses and using service protocols seem necessary to reduce errors. A daily ASP could also improve compliance in these error-prone situations. Trial registration: This trial was approved by Toulouse University Hospital, and is registered in its register of data study, number RnIPH2019-79, and with ClinicalTrials.gov, number NCT04642560. The date of first trial registration in ClinicalTrials.gov was 24/11/2020.