Background: Inverted papilloma (IP) is a benign lesion of the nasal cavity and paranasal sinuses. The aetiology of IP remains unclear. Objective: To assess whether the sinonasal bacteriology of patients with IP is different from the bacteriology of chronic rhinosinusitis (CRS) patients and if there are differences between primary and recurrent IP. Methodology: A retrospective review of patients with IP at a tertiary referral centre. Intraoperative microbiology results from primary and revision IP resections were compared to each other and to published microbiology data from CRS patients. Results: Twenty-six cases of IP were identified with a total of 83 intraoperative cultures, of which 43 were positive. The most common isolates were coagulase negative Staphylococcus (SCN), Propionibacterium, Staphylococcus aureus, and Streptococcus. The trends in the prevalence of isolates were similar to those reported for CRS patients. Additionally, similar bacteriology was identified between primary and revision IP patients. Conclusion: In our series, the most common bacterial isolates found in IP are similar to those of CRS, as is the prevalence of gram-negative organisms. Additionally, we did not demonstrate a difference between primary and recurrent IP. Our findings suggest that IP does not result from specific sinonasal microbial exposure.