Aim This study aimed to investigate montelukast (MONT), a leukotriene receptor antagonist, as a potential treatment protocol and/or supportive therapy against acute bacterial sinonasal inflammation by histopathological and molecular analyses. Material and Methods A total of 30 rats were used in the study. The nasal dorsum was sterilized, and gelatin sponges were inserted into the right nasal cavities. The nostrils were then inoculated with Staphylococcus aureus (SA) for rhinosinusitis (RS) induction. Rats were treated once daily for 7 days with an injection of saline, either cefazolin sodium (CEFA) or MONT. Tissue samples were collected for examination. Results To evaluate whether CEFA and MONT were able to attenuate the SA-induced nasal inflammation, we analyzed the proinflammatory cytokine levels in the nasal tissue of rats by real-time polymerase chain reaction (PCR). The inflammatory cytokines tumor necrosis factor-α ( P ≤ .05) and interleukin-1α (IL-1α) ( P ≤ .05) increased in the SA-induced group, when compared with the healthy control. MONT treatment significantly reversed these elevations, especially IL-1α messenger RNA expression levels induced by SA. Also, CEFA administration significantly changed the proinflammatory cytokine levels when compared to the SA group, but this effect was not as strong as MONT. Also, histopathological findings supported the beneficial effects of MONT. Conclusion This study histopathologically and molecularly showed that MONT significantly ameliorated the SA-associated sinonasal inflammatory reaction, both alone and in combination with CEFA. These results may suggest that MONT may block the inflammatory reaction underlying RS even more significantly by antioxidative or anti-inflammatory effects. This study suggests MONT as a future potential therapeutic agent for RS treatment.