Sweet oranges are prone to spoilage by filamentous fungi as a result of their high levels of sugars and low P H values. These fungi are known to produce toxins which are deleterious to human health. This study was therefore conducted to isolate, characterize and identify the filamentous fungi associated with the spoilage of sweet oranges sold in major Awka Markets, Nigeria. Thirty sweet orange fruits purchased from Eke-Awka, Temporary Site, Nodu, Ifite and Amaenyi Markets were used for the study. The average filamentous fungal count of the spoilt sweet orange fruits was 2.0 x10 3 cfu/ml, 1.3 x 10 3 cfu/ml, 2.1 x 10 3 cfu/ml, 1.6x 10 3 cfu/ml and 1.8 x 10 3 cfu/ml for the samples from Eke-Awka, Temporary Site, Nodu, Ifite and Amaenyi Markets respectively. The fungi were identified as Aspergillus niger, Rhizopus stolonifer, Mucor mucedo, Penicillium digitatum, Fusarium oxysporum and Aspergillus flavus. The percentage distribution of the fungi was 27.5%, 22.5%, 15.0%, 10.0%, 7.5 and 17.5% for Aspergillus niger, Rhizopus stolonifer, Mucor mucedo, Penicillium digitatum, Fusarium oxysporum and Aspergillus flavus respectively. Aspergillus niger caused the highest degree of spoilage. Good agricultural practices, adequate storage facilities and good handling practices must be put in place to reduce the incidence of these fungi in sweet oranges thereby minimizing their spoilage.