Purpose: . Interfacial microleakage between dental implant and its abutment has been reported as a source of bacteria which can cause peri-implantitis and persistent inflammation, and abutment screw is on the pathway of this contamination. The aim of this study was to evaluate the antibacterial effect of nano-silver coating on the abutment screw against bacteria proliferation. Materials and methods: . Titanium abutment screws were coated with silver in nano particle level by sputtering method. The coated screws were examined with SEM and their surface composition were analyzed with EDS. Leakage of metal ions/particle was examined with inductively coupled plasma optical emission spectrometry. To evaluate antibacterial effect, abutment screws with/without coating were contaminated with P. gingivalis, S. sanguinis, T. denticola, T. forsythia for 48 hours. Then their antibacterial effect was evaluated with real-time PCR by comparing the total genomic DNA concentration and 16S rRNA derived cDNA concentration, and effect was confirmed with fluorescent staining technique which enables segregation between live and dead cells. Results: . The coating was in even layer with nano sized silver particles (mean particle size 28 nm in diameter) and showed 0.53 µg leakage for 24 hours per screw. The antibacterial effect of the coated group on the tested bacteria resulted in a decrease in the Viable/Total ratio of approximately 86% for P. gingivalis, 89% for S. sanguinis, 61% for T. denticola, and 97% for T. forsythia. The results were statistically significant (P < .05). The microscopic images confirmed anti-bacterial effect of the coated abutment screw. Conclusion . Within the limit of this study, nano-silver coating on the abutment screw may damage the viability of P. gingivalis, S. sanguinis, T. denticola, T. forsythia. Silver coating on the titanium abutment screw can be considered as an effective method to give antibacterial effect.