Nigeria is in the process of strengthening yellow fever case-based surveillance with the collection of serum samples among suspected case patients. Atraining conducted for surveillance officers in the local government areas (LGAs) of Osun State on yellow fever case-based surveillance was assessed to determine its immediate impact on the knowledge of participants. The training focused mainly on how to detect and report a suspected case of yellow fever to the national authorities and the reference laboratory. Training materials included theWorld Health Organization district guidelines for yellow fever surveillance.Apre and post test was used to evaluate the immediate impact of the training on knowledge among participants. Atotal of 31 officers participated. The mean scores for pre and post tests were 7.1 (SD 3.6) and 20.7 (SD 3.4) out of a total of 30 points respectively. More than 80% of participants rated the training as excellent in overall organization.All participants indicated that they were very confident to fully implement yellow fever surveillance in their LGAs