Introduction: Nasal polyp is an inflammatory condition of unknown etiology with a prevalence rate of about 4%. Unilateral nasal polyp is common in the ear, nose, and throat (ENT) practice and publications in the literature in this regard are few. Aim: The aim of this study was histological analysis of eosinophil cells in unilateral nasal polyp and to correlate its relationship of allergic etiology with unilateral nasal polyp. Materials and methods: The study conducted was a retrospective study where 70 patients diagnosed as unilateral nasal polyp were analyzed with their histopathology reports. It included patients of either sex with age between 6 and 65 years. All these patients had undergone surgery and polyp specimen was sent for histopathological examination. The patients were grouped as per their histopathological diagnosis as inflammatory polyp with tissue eosinophil and inflammatory polyp without tissue eosinophil and were compared. Tissue eosinophil grading was done according to Shioda and Mishima system. Data were analyzed and a conclusion was drawn. Results: In total 70 patients (100%) of unilateral nasal polyp, 33 patients (47%) showed presence of tissue eosinophil and 37 patients (53%) showed absence of tissue eosinophil in histopathological examination. Out of 33 patients with tissue eosinophil, 16 patients (48.5%) showed significant tissue eosinophil with p < 0.0000. Conclusion: Since the p-value is significant in our study, otorhinolaryngologists should consider allergy as an etiological factor in the management of unilateral nasal polyp.