The oral cavity is perpetually colonized by different species of microorganisms and at times it is difficult to characterize the periodontal pathogen causing breakdown of tissue and bone. But over the years, based on scientific knowledge, it has been observed that various gram negative anaerobic bacteria have been involved with the initiation of periodontal disease. Based on literature reviews, a study was undertaken to investigate the antimicrobial effect of Anacardium occidentale (cashew) leaf extract on Porphyromonas gingivalis and Prevotella intermedia. Methanol and aqueous extracts of cashew leaves were prepared. Its antimicrobial activity against P. gingivalis and P. intermedia was tested using the agar diffusion method at various dilutions of 75 μ, 50 μl, 25 μl, 10 μl and 5 μl respectively. 0.2% Clorhexidine gluconate (CHX) was used as control. Cultures of P. gingivalis and P. intermedia strains were maintained on Kanamycin blood agar. The agar plates were then incubated at 37?C for 72 hours after which the zone of inhibition was measured and the mean was recorded for each test solution. The results of this study demonstrated that, for both P. gingivalis and P. intermedia, the highest concentration (75 μl) of both the extracts showed maximum antimicrobial action. For P. ginigvalis, the aqueous extract demonstrated significant inhibitory activity compared to the methanolic extract (p = 0.005), which was comparable to that of CHX. For P. intermedia, similar results were observed with aqueous extract being more effective compared to methanolic (p = 0.007), however, CHX was most effective compared to both the extracts (p = 0.007). This study revealed that Anacardium occidentale leaf extracts have efficient antimicrobial activity against P. gingivalis & P. intermedia. Hence, this preliminary study suggests that the antimicrobial action of A. occidentale leaf could be utilized for the preparation of chemical plaque control formulations.