Aim: To investigate the antimicrobial properties of calcium hydroxide when mixed with three vehicles namely Zamzam water, Normal saline and 2% Chlorhexidine. Materials & Method: 6 plates of nutrient broth and S. aureus culture were prepared. 2 (5*3 mm) wells were prepared in one plate and is used as control. 3 wells each were prepared in the remaining 5 plates and filled with freshly prepared mix of calcium hydroxide with the three vehicles (5 wells were filled with each mix). The same process was repeated using 6 plates containing nutrient broth and B. subtilis culture. The plates were then incubated for 24 hours and the Zone of inhibition (ZOI) was measured. The pH of each mixture was also measured by using a pH meter. The data was analyzed by ANNOVA test and compared by using Tukey HSD test. Result: The mean value of ZOI for Ca(OH2) and Zamzam was statistically significant when tested against both the bacteria. The pH of 12.26, 11.90 and 12.10 was achieved for Ca(OH2) and Zamzam, Ca(OH2) and Normal saline and 2% Chlorhexidine and Ca(OH2). Conclusion: Calcium hydroxide powder mixed with Zamzam water exhibited the highest pH of 12.26 and showed statistical significant antimicrobial difference when compared to other medicaments. However further in depth scientific investigations regarding the properties and safety of Zamzam water and World health organization (WHO) approval would be required before considering its clinical use. Clinical significance: Persistence of infection after cleaning and shaping of the canals is attributed to the presence of bacteria which necessitates the use of an antimicrobial agent as a inter appointment dressing. Calcium hydroxide was considered gold standard intra canal medicament due to its high alkalinity. A proper vehicle is necessary to activate the calcium hydroxide by releasing the Ca+ and OHions. The results of this study showed that Calcium hydroxide powder mixed with Zamzam water exhibited the highest pH of 12.26