© 2018 ARS-AAOA, LLC Background: The ciprofloxacin-coated sinus stent (CSS) has unique therapeutic potential to deliver antibiotics to the sinuses. The objective of this study is to evaluate the efficacy of the CSS stent in eliminating Pseudomonas aeruginosa infection in a rabbit model of sinusitis. Methods: A ciprofloxacin-eluting sinus stent was created by coating ciprofloxacin/Eudragit RS100 on biodegradable poly-D/L-lactic acid (2 mg). After analyzing in-vitro inhibition of P aeruginosa (PAO-1 strain) biofilm formation, a total of 8 stents (4 shams, 4 CSSs) were placed unilaterally in rabbit maxillary sinuses via dorsal sinusotomy after inducing infection for 1 week with PAO-1. Animals were assessed 2 weeks after stent insertion with nasal endoscopy, sinus culture, computed tomography (CT) scan, histopathology, and scanning electron microscopy (SEM). Results: PAO-1 biofilm formation was significantly reduced in vitro with exposure to the CSS (p < 0.0001). Insertion of the stent in PAO-1–infected rabbits for 2 weeks resulted in significant improvement in sinusitis according to endoscopy scoring (p < 0.0001) and CT scoring (p < 0.002). Histology and SEM revealed marked improvement in the structure of the mucosa and submucosa with no detection of biofilm structures in the CSS cohort. Conclusion: Although this study had a small sample size, we identified robust therapeutic efficacy of the CSS by reducing bacterial load and biofilm formation of P aeruginosa in a preclinical model of sinusitis after placement for 2 weeks.