Background: Aspergillus is a fungus which may present an array of pulmonary manifestations, depending on the patient's immunological and physiological state. Although the incidence of pulmonary aspergillosis occurs primarily in immunocompromised patients but the incidence is also rising in immunocompetent individuals, especially in developing countries. Aim: The objective of the study was to determine the prevalence and predisposing factors of pulmonary aspergillosis along with species identification. Materials and Methods: One hundred and three patients admitted to the Department of Chest and Tuberculosis and in the Department of Medicine from Jan 2012 to Jan 2013 were included in this study. The patients were epitomized on the basis of clinical signs and symptoms, physical examination, chest radiography, CT scans, histopathological examination, bronchoscopy and fungal examination including potassium hydroxide mount, fungal culture of sputum and bronchoalveolar lavage. Species identification was done by colony characteristics, slide culture and Lactophenol Cotton blue mount. Results: Out of the 103 patients, (63 males and 40 females) Aspergillus species has been isolated from 17 (16.5%) males and 07 (6.79%) females. Various predisposing factors of pulmonary aspergillosis have been identified in which pulmonary tuberculosis, chronic smoking and environmental exposure to asbestos, cement its tops the list. Many of the patients had multiple predisposing factors. Aspergillus species were isolated in 24 (23.3%) cases. Aspergillus fumigatus was the predominant species isolated in 13 (54.16%) cases followed by Aspergillus flavus in 07 (29.16%) cases, Aspergillus niger in 03 (12.5 %) and Aspergillus terrus in 1 (4.16%) cases. Conclusion: It is concluded that the prevalence of pulmonary Aspergillosis is quite high in immunocompromised individuals and low in immunocompetent individuals. An adequate and efficient evaluation of the etiological agents has a crucial role in the management of such patients.