Abstract : This study aimed to evaluate the ability of negative pressure irrigation technique (NPI) compared to the positive pressure irrigation technique (PPI) in eradication of Enterococcus faecalis inside infected and minimally prepared root canals. 40 extracted premolars were decoronated, instrumented up to size #20 with a taper of 0.04 (minimal preparation), autoclaved and inoculated with Enterococcus faecalis for 15 days, divided into two equal groups according to the irrigation method used: Group 1 (Experminteal, n=20): irrigation by NPI, and Group 2 (Control, n=20): irrigation by PPI. After irrigation, microbial samples were collected, transferred to nutrient agar and incubated for counting of bacterial colony forming units (CFUs) Data were analyzed using dependent and independent sample t-test. The results showed a significant decrease in the mean number of CFUs by both NPI and PPI methods (p=0.000), and the mean number of CFUs after irrigation with NPI was lower than PPI method (p=0.043). Both irrigation methods were effective in reducing the bacterial count, but NPI shows greater effectiveness in reducing the bacterial count in the minimally prepared root canals and infected with Enterococcus faecalis.