Due to increasing problems of the resistance associated with praziquantel, the drug of choice for treatment of schistosomiasis, alternative therapies were tried. The present work evaluated the effect of iron nanoparticles (iron NPs) on S. mansoni and B. alexandrina in vitro. The mortality rate of adults was observed after exposure during a period of 48 hrs. Worms exposed to 30 & 60mg/L of iron nanoparticles showed 20% & 77% mortality after 3 hrs, respectively. Snails exposure to different concentration of iron NPs (1- 40mg/L) died (100%) at, 40mg/L after 24 hours of exposure. The commonest surface ultrastructural changes were exposing of blebs everywhere, cracks, erosion, and incomplete fusion of some tubercles that lost most of their spines. Perforation was noticed on some areas of the tegument. The ventral sucker sinks incompletely inside the tegumental surface, sloughing was observed and perforation was noticed on the body surface. Also, collapsed tegumental architecture, huge oedematous structures were lounged from collapsed tegument.