Objective: This study was conducted to assess the level of knowledge of influenza A (H1N1) infection among health care workers in a secondary health care facility in Osogbo, Southwest Nigeria. Methods: A structured questionnaire assessing participants' knowledge of swine influenza viruses, mode of transmission, clinical criteria, primary prevention, indications for emergency care, care of affected persons and ongoing pandemic of Influenza A H1N1 was hand-delivered to all senior health care workers working in the hospital. Results: The mean age of the respondents was 40.4 +/- 9.6 years. The majority (59.3%) were females. Television (73.6%) radio (61.5%), newspapers (44%), other health workers (31.9%), and internet (15.4%) were the main sources of information about influenza A H1N1. Nearly all (92.3%) felt that their source of information about the disease was inadequate. About half (51.6%) knew the virus can be transmitted from one person to another. Majority identified correctly the symptoms of infected victims such as fever (83.5%), and runny nose (79.1%). Most (87.9%) identified hand washing with soap and water as a mode of preventing transmission. Most (83.5%) felt an infected person should be isolated while very few knew oseltamivir (13.2%) and zanamivir (17.6%) are drugs to treat. Multivariate linear regression analysis identified, male sex (p=0.029), internet as a source of information (p=0.029) and knowledge of prevention of H1N1 (p=0.005) as factors that were significantly associated with a high knowledge score on the current pandemic. Conclusion: There is a need to provide comprehensive information to health workers on the current pandemic.