Objective: Green synthesis, characterization of silver nanoparticles (AgNPs) and study of the synergistic effect of AgNPs with antibiotic doxycycline against Klebsiella pneumonia. Methods: AgNps were synthesized from bacteria isolated from samples obtained from petroleum soil. After characterization of the nanoparticles, the antibacterial activity of the nanoparticle was studied, and ... [Show full abstract] simultaneously the same nanoparticle was used in combination with doxycycline antibiotic. Results: It was observed that compared to the effects of AgNps and antibiotic alone, the collective effect on both of them was more evident, which indicate the synergistic effect of the two components. Conclusion: These findings highlight the potential for AgNPs to enhance the activity of doxycycline antibiotic against Klebsiella pneumonia infections.