The natural fibre concrete may undergo a reduction in strength as a result of weakening of fibres by the combination of alkali attack and environmental loads. Silica fume slurry treatment is one of the best way to improve the durability of natural fibres in concrete. In this paper, fibre reinforced concrete with natural fibres such as coir and sugarcane baggase of as received condition and silica fume treated were cast at three volume fractions, 0.5%, 1.0% and 1.5% and tested to study the chloride resistance. This experimental program consists of determination of mass loss and strength deterioration against hydrochloric acid attack, rapid chloride penetration and . From the studies, 10 to 20% reduction due to hydrochloric acid attack and 15 to 25% reduction due to freezing and thawing were observed in concrete with as received natural fibres. Concrete with treated natural fibres showed a better resistance against all the durability effects.