The present study was carried out to evaluate in-vitro toxicity associated with chitosan nanoparticles, Gantrez nanoparticles and poly-lactide co-glycolide (PLG) microparticle in Vero cell line. The cytotoxicity of all three micro/nano-particles was assessed using different concentration. For each concentration, the confluent monolayer was treated for a period of 36-48 hours and studied for morphological alteration, live and death count etc. after the treatment. It was observed that the different concentrations of chitosan nanoparticles and Gantrez nanoparticles did not have significant effect on the cell viability as evident from the non-significant difference between the OD540 of formazan product formed from MTT in treated and untreated cells. The concentration of chitosan nanoparticles and Gantrez nanoparticles up to 1000 micrograms/ml did not have any influence in cellular metabolic activities and viability. However, a reduction in the cellular viability and metabolic activities were observed when PLG microparticles were used at 1000 micrograms/ml. At concentrations below 1000 micrograms/ml, all the nanoparticles/microparticles were found to be safe in terms of cytotoxicity.