This study investigated the factors associated with fish spoilage among fish mongers in Ogun Waterside Local Government Area, Ogun State. The study also identified different fish processing and preservation methods used by fish mongers. Three communities were purposively selected out of 23 fishing communities due to their nearness to water resources. A simple random sampling technique was used to select 114 respondents from a total of 570 registered fish mongers. Descriptive statistics such as frequency counts and percentages were used to summarize the data while inferential statistical tool used to analyze the data was Chi square. The results show that 38.6% of the respondents were within the age category of 30-39. Fish mongers were female dominated (75.4%), 35.1% of the respondents had no formal education and 65.8% were married. The most important processing and preservation method was smoking (88.6%). Factor associated with fish spoilage were lack of equipment for processing and storage (54.0%), and inadequate access to loan and credits (51.0%). Chisquare analysis showed that sex, educational level and marital status (Cal. χ2 6.44 Tab. χ25.991, Cal.χ225.968 Tab.χ215.507,Cal.χ2 29.107 Tab.χ2 18.307) were all statistically significant to factors associated with fish spoilage. It is concluded that lack of equipment for processing and storage and inadequate access to loan and credits contributed to fish spoilage. Therefore, efforts at providing equipment for processing and access to loan and credits should be given attention.