Hymenolepis nana (H.nana) is the most common tapeworm infection worldwide. It is more prevalent in warm climates where sanitation is poor, particularly among children. The effect and mechanism of action of praziquantel (PZQ), given at a dose of 25 mg/kg BW, and C.papaya dried seed crude aqueous extract (CAE), given at a dose of 1.2 gm/kg BW, were assessed on H.nana worms in experimentally infected mice. Tegumental changes were studied using the scanning electron microscope (SEM) and different parasitological parameters were also observed. Each group of infected mice was divided into two subgroups. The first subgroup received either treatment before the 4th day after infection to investigate their effects on cysticercoid stage. The other subgroup received treatments after the development of the adult stage, confirmed by egg detection in stool. Both PZQ and C.papaya dried seed CAE resulted in significant reduction of worm burden, total egg output and viable egg count. Marked tegumental changes were evident in adult worms treated with either treatment. However, all previous effects were exerted more rapidly in case of PZQ treatment. They both significantly reduced cysticercoid stage size. However, C.papaya outstand PZQ in having a deforming effect on adults arising from treated cysticercoids. C.papaya has significant anti-cestodal properties that enable its seed extract to be a very effective alternative to PZQ against H.nana.