OBJECTIVE: The aim of this study was to evaluate the demographic data, molecular epidemiology, and in vitro antifungal susceptibility results of patients with Aspergillus isolated from various clinical specimens. METHODS: A total of 44 Aspergillus strains were studied. The definition of invasive aspergillosis in patients was made according to European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria. Strains were phenotypically and molecularly identified. Demographic characteristics of patients and genotypes of strains were evaluated. Phylogenetic analysis was done by the The Unweighted Pair-Group Method with Arithmetic Mean (UPGMA). Antifungal susceptibility of strains was determined according to The Clinical and Laboratory Standards Institute (CLSI)-M61-Ed2 and The European Committee on Antimicrobial Susceptibility Testing (EUCAST). RESULTS: A total of 11 patients were classified as proven and 33 as probable invasive aspergillosis. There was a statistically significant difference in age groups, subdisease, neutropenic, and receiving chemotherapy between groups. A total of 23 strains were identified as Aspergillus fumigatus, 12 as Aspergillus niger, 6 as Aspergillus flavus, and 3 as Aspergillus terreus. Phylogenetic analysis revealed five different genotypes. No statistical difference was found in the comparisons between patients groups and genotype groups. There was a statistically significant difference between genotype groups and voriconazole, posaconazole, and itraconazole Minimum Inhibition Concentration (MIC). CONCLUSION: Accurate identification of strains and antifungal susceptibility studies should be performed due to azole and amphotericin B resistance. Genotyping studies are important in infection control due to identifying sources of infection and transmission routes.