This work aimed to study the effect of host biological factors on the different parasitic helminthes in Clarias gariepinus from Lake Manzala. The sex, weight and length of fish were determined. Examination of C. gariepinus fish for helminthes revealed the presence of three morphologically distinct adult helminthes in the digestive tract which were Polyonchobothrium clarias and Monobothrium wageneri (Cestodes) and Neoechinorhynchus rutili (Acanthocephala) and there were also the cestodes larvae (Plerocercoid) and undifferentiated cestodes. Two types of defined mataceracariae were observed in the different tissues which were Ornithodiplostomum sp. and Prohemistomum sp. (trematodes). The undifferentiated metacercariae were also recorded. Results showed that the highest prevalence of infection was found in smaller fish (weight and length) and in females (sex). The occurrence of each of the helminthes gives a different response to these factors as discussed in this work.