Background: One cause of fish disease is the Argulus parasite. Both male and female Argulus were found to infect fish. This study aims to determine the percentage difference of male and female Argulus that infect Cyprinidae in Magelang Regency. Methods: The present study used a survey method. The independent variables in this study are carp (Cyprinus carpio), goldfish (Carassius auratus), comet goldfish (Carassius auratus), koi fish (C. carpio koi) and the sex of the Argulus parasite. The dependent variable of this study was the sex percentage of the Argulus parasite. The data analysis was done using analysis of variance (ANOVA) then followed by Duncan’s multiple range test to find out the differences between treatments. Result: The first ANOVA result showed no significant difference (p greater than 0.05), the second ANOVA showed significantly different results (p less than 0.05) and the third ANOVA reveals no significantly different percentage (p greater than 0.05). The highest infestation rate of male Argulus japonicus is found in koi fish (C. carpio koi) is 60% and the lowest is in comet goldfish, which is 38.46%. Whereas infestation of female A. japonicus in carp, goldfish, comet goldfish and koi fish also obtained a similar result.