ABSTRACT. – Twelve specimens of Heterobranchus longifilis sampled from the River Boumba were examined for their monogenean gill parasites. Quadriacanthus longifilisi N’Douba, Lambert & Euzet 1999 and Q. thysi N’Douba, Lambert & Euzet 1999 are newly recorded in the studied locality. Three new species have also been described: Q. tricorniculai n. sp., Q. triunguisi n. sp., and Q. ndoubai n. sp. Quadriacanthus tricorniculai and Q. triunguisi are characterized by the unique morphology of their accessory pieces, which end in a three-head hydrashaped structure, with tentacles being longer in Q. tricorniculai; proximal extremity of accessory piece is stronger for Q. triunguisi, while Q. ndoubai is distinguished by the size of its male copulatory organ (larger than 80 μm) and the fork shaped distal extremity of the accessory piece of the male copulatory complex. The variability of monogenean species richness of Heterobranchus longifilis between Ivory Coast and Cameroon is discussed.