Abstract Giardia lamblia is one the most common human zoonotic protozoan affecting about 200 million people annually, But recurrent symptoms and drug resistance were reported in giardiasis patients. The present study assessed the therapeutic effect of Tomex® and probiotics against giardiasis as well as evaluated efficacy of chitosan nanoparticles and metronidazole. Sixty healthy male hamsters were divided into 6 groups. Each group consists of 10 hamsters as following: GI non-infected hamsters, GII infected control, GIII, GIV, GV & GVI infected with G. lamblia and treated with tomex, probiotics, chitosan nanoparticles (CsNPs), and metronidazole (MTZ) respectively. Hamsters were orally infected with 10,000 Giardia cysts. After 3 weeks stool samples were examined for Giardia samples and contents for intestinal histopathology and electron microscopy of Giardia trophozoite ultrastructure. The highest reduction in Giardia cyst and trophozoite were in hamsters received MTZ but with natural alternative therapies chitosan nanoparticles showed a therapeutic effect with highest reduction in cyst and trophozoite counts (80.59% & 76.55%) respectively and best recovery in intestinal pathology. MTZ gave higher reduction rates (91.04% & 90.75%) respectively with normal intestinal histopathology.