Background & Objective: Doxycycline, a broad-spectrum antibiotic, is the most commonly prescribed antibiotic worldwide for treating infectious diseases. The newly used nanoparticles loaded with the antibiotics have been introduced in the treatment of many infections. The aim of the present study was to compare between the antibacterial effect of doxycycline, silver nanoparticles and doxycycline carried on silver nanoparticles on Aggregatibacter Actinomycetemcomitans (A. Actinomycetemcomitans) in vitro. Materials and Methods: Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) for the antibiotic, silver nanoparticles and the combined use of nanoparticles and antibiotics were determined. Tube dilution methods were performed and weighted in an analytical balance. Results: Doxycycline loaded in Silver Nanoparticles was the most efficacious with a MIC of 1μg /ml for doxycycline and MIC of 0.2μg/ml for silver nanoparticles while the MIC was0.8μg/ml for silver nanoparticles and 2μg/ml for Doxycycline. In group III (Doxycycline loaded in Silver Nanoparticles) the reduction in number of A. actinomycetemcomitanswas significantly greater than two other groups. Conclusion: Silver nanoparticles have antimicrobial effect on A. actinomycetemcomitansand thus increase the effectiveness of the loaded antibiotics. So that low concentrations of antibiotics, along with silver nanoparticle has the same effect of high dose antibiotics.