This study deals with the evaluation of chloride ion penetration on calcined bentonite modified concrete. The variables in this work were taken as bentonite replacement and calcination temperature. 0, 5, 10, 15 percentage of bentonite was replaced in concrete at calcination temperature of 7000C and 8000C. 64 specimens were cast as per the mix design was prepared by using the standard procedure IS 10262. Specimens were tested after 7 days and 28 days of curing. Concrete modified with 5% of bentonite at 8000C performed better results among all mixes. This may be attributed to the better fineness of calcined bentonite