The purpose of this study was to compare the antibacterial efficacy of Green Tea extract (GT, camellia sinensis) and 5.25 % Sodium hypochlorite (NaOCl) as root canal irrigants, evaluate the effect of GT on dentin hardness compared to NaOCl, and also study the cytotoxic effect of GT on fibroblast compared to NaOCl. Dried and ground Green tea leaves were extracted with 70% ethyl alcohol/water with the ratio 1:5.The mixture was stored in the darkness for two weeks, and then filtered through filter paper. The filtrate was kept in the fridge and the residue was re-macerated in the same solvent for another week and filtrated the same way. The resulting filtrate was combined with the first filtrate. The combined filtrate was evaporated using Rotavapour® at 50° untill dryness. The resulted crude extract was weighed to calculate the percentage, and different concentrations were prepared; i.e 3%, 6%, 12%. In this study, 80 human single rooted teeth were inoculated with E.Faecalis and incubated for one week. Teeth were then prepared by using protaper rotary files, both shapers and finishers and irrigated with the tested irrigants; group 1: saline, group 2: 5.25% NaOCl, group 3: 3%GT, group 4: 6%GT, group 5:12% GT. Samples were collected and smeared on agar plates, then plates were incubated for 24 hours. E.facalis colonies were counted by visualization of white pin point colonies, then the number of CFU/samples was calculated. Summary and conclusion 88 1.While in the dentin hardness test, 80 teeth were split longitudinally into halves and measurements were taken before and after samples were treated using different irrigants using Vickers hardness test. For the cytotoxicity test, irrigants were tested against hamster kidney fibroblasts cell line. The results of the present study revealed the following: The highest statistically significant antibacterial activity of the irrigants was observed for 5.25% NaOCl solution followed by 12% GT, 6% GT and 3% GT respectively, while saline showed no antibacterial activity. In the cytotoxicity test, NaOCl and 12% GT showed the least statistically significant cell viability, followed by 6 % GT and 3 % GT without statistical significance between them. 5.25 % NaOCl showed the highest statistical significant dentin hardness decrease, followed by 12 % GT, while 6 % GT and 3 % GT showed insignificant increase in dentin hardness. No dentin hardness change was observed in saline group.