BACKGROUND Numerous antimicrobial agents are used to eliminate oral biofilm. However due to emergence of multi drug resistant microorganisms, the quest to find out biologically safe and naturally available antimicrobial agents continues. OBJECTIVE To evaluate antimicrobial efficacy of silver nano-particles against five common oral pathogenic bacteria. OBJECTIVE To determine antimicrobial activity of silver nanoparticles and chlorhexidine gluconate against oral pathogenic bacteria. METHODS We used strains of Streptococcus mutans (MTCC 497), Streptococcus oralis (MTCC 2696), Lactobacillus acidophilus (MTCC 10307), Lactobacillus fermentum (MTCC 903), and Candida albicans (MTCC 183). We used commercially available silver nanoparticles (experimental group) and chlorhexidine gluconate (positive control). We determined minimum inhibitory concentration (MIC) minimum bactericidal concentration (MBC) of both agents and analyzed the data using paired 't' test, one way ANOVA and Tucky's post Hoc HSD. RESULTS Silver nanoparticles inhibited bacterial growth moderately. The mean MIC of AgNP against S. mutans was 60 ± 22.36 μg/ml, S. oralis - 45 ± 11.18 μg/ml, L. acidophilus - 15 ± 5.59 μg/ml, L. fermentum - 90 ± 22.36 μg/ml, Candida albicans - 2.82 ± 0.68 μg/ml respectively. For chlorhexidine gluconate, mean MIC for S. mutans was 300 ± 111.80 μg/ml, S. oralis - 150 ± 55.90 μg/ml, L. acidophilus - 450 ± 111.80 μg/ml, L. fermentum - 450 ± 111.80 μg/ml and Candida albicans - 150 ± 55.90 μg/ml. MIC and MBC values of AgNP were significantly lower than chlorhexidine gluconate and statistically significant (p < 0.05). CONCLUSIONS Silver nanoparticles exhibited better bacteriostatic and bactericidal effect with concentration less than five folds as compared to chlorhexidine. Silver nanoparticles when used in appropriate concentration as safe alternative to present chemically derived other antimicrobial agents.