Purpose Duration of antibiotic therapy for ventilator-associated pneumonia (VAP) due to non-fermenting Gram-negative bacilli (NF-GNB), including Pseudomonas aeruginosa (PA) remains uncertain. We aimed to assess the non-inferiority of a short duration of antibiotics (8 days) vs. prolonged antibiotic therapy (15 days) in VAP due to PA (PA-VAP). Methods We conducted a nationwide, randomized, open-labeled, multicenter, non-inferiority trial to evaluate optimal duration of antibiotic treatment in PA-VAP. Eligible patients were adults with diagnosis of PA-VAP and randomly assigned in 1:1 ratio to receive a short-duration treatment (8 days) or a long-duration treatment (15 days). A pre-specified analysis was used to assess a composite endpoint combining mortality and PA-VAP recurrence rate during hospitalization in the intensive care unit (ICU) within 90 days. Results The study was stopped after 24 months due to slow inclusion rate. In intention-to-treat population ( n  = 186), the percentage of patients who reached the composite endpoint was 25.5% ( N  = 25/98) in the 15-day group versus 35.2% ( N  = 31/88) in the 8-day group (difference 9.7%, 90% confidence interval (CI) −1.9%–21.2%). The percentage of recurrence of PA-VAP during the ICU stay was 9.2% in the 15-day group versus 17% in the 8-day group. The two groups had similar median days of mechanical ventilation, of ICU stay, number of extra pulmonary infections and acquisition of multidrug-resistant (MDR) pathogens during ICU stay. Conclusions Our study failed to show the non-inferiority of a short duration of antibiotics in the treatment of PA-VAP, compared to a long duration. The short duration strategy may be associated to an increase of PA-VAP recurrence. However, the lack of power limits the interpretation of this study.