Abstract : Herbal extracts exhibited a worth noticed antimicrobial activity against wide range of microorganisms. Apparent worldwide interest in the production of high value phytochemicals, this new approach of using natural remedies termed phytotherapy or ethnopharmacology. Root canal treatment protocols require the application of effective intracanal medicaments especially in cases with infected or previously treated canals in order to eradicate resistant microorganisms and maximize the success rate of the treatment. Nasturtium officinale is a plant with documented beneficial properties. Many studies investigated its antimicrobial properties and the results were positive. The aim of the study was to investigate the antibacterial activity of the alcoholic extract of Nasturtium officinale (watercress) alone and in combination with calcium hydroxide against Enterococcus faecalis as intracanal medication. Enterococcus faecalis is widely recovered from infected canals and regarded the most commonly isolated bacterial species from failed treated cases. The sensitivity of this bacteria to different concentrations of alcoholic extract of Nasturtium officinale was determined by using agar well diffusion method in comparison to calcium hydroxide paste. The minimum bactericidal concentration (MBC) of the tested extract against the isolated bacteria was obtained by agar plate method. Another experiment involving testing the combination of the extract with calcium hydroxide was evaluated and compared to calcium hydroxide paste with iodoform. The results of the study were promising and the extract exhibited an antibacterial activity against Enterococcus faecalis by formation of growth inhibition zones. The highest concentration tested (20 mg/ml) demonstrated the largest diameter of inhibition zones in Muller Hinton Agar plates. The studied combination with calcium hydroxide revealed a positive reaction. In conclusion, alcoholic extract of Nasturtium officinale proved to have effective antibacterial activity against Enterococcus faecalis and the combination led to enhancement of the antibacterial activity of calcium hydroxide.