Introduction and Aim:Nanoparticles for some metals can be used in the treatment of diseases caused by different pathogenic bacteria that are resistant to antibiotics due to the antibacterial properties of thesenanoparticles.In the current study, thesynthesis of silver nanoparticles (Ag) from Cinnamon zeylanicum bark extractwas investigated.   Materials and Methods:One mL of cinnamon bark extract was added to 50mL of 1mM of the silver nitrate (AgNO3). After incubation time of bark extract with AgNO3at room temperature for 1-18hours, the silver nanoparticles synthesis through changed colour of the mixture to dark brown.The UV, TEM and FT-IR analysis were carried out to characterize the biosynthesized Ag-NPs, UV-Vis scan showed absorption around 435 nm while TEM showedAg-NPs spherical shape and the sizes of the and FT-IR spectrum detected the presence of different functional groups responsible for reduction and stability of Ag-NPs in an aqueous solution.   Results:Biosynthesized Ag-NPs showed inhibitory effect against someGram-negative bacterial species that have complete resistance to the antibiotics P, NA, VA, E, TE. The inhibition zone of Ag-NPs wasdetermined as follows (Citrobacter freundii19mm, Klebsiella pneumonae23mm, E.coli 23mm, Enterobacter spp 20 mm, Acinetobacter baumannii20mm.Therefore, Ag-NPs can be used as alternative treatment for some antibiotics.   Conclusion: The Ag-NPs can be successfully prepared form Cinnamomum bark plant. Besides their low cost, these NPs had an antibacterial effect especially against Gram negative bacteria which had a complete resistance to the most common antibiotics