This paper presents an experimental investigation on the performance of two groups of RC circular columns wrapped with Carbon Fiber Reinforced Polymer (CFRP) was studied under two different types of environments for a period of (4 months). The first group of RC columns was exposed to tap water (W), while the second group was exposed to sulfate solution (M) (15% MgSO4). The results of the study showed that the sulphate attack significantly decreased the strength of the unstrengthen columns by up to (14.29%), while its impact was less on the strength of the strengthened columns with (one CFRP layer) was (10.20%) compared with the columns under tap water. The effect of sulfate attack decreases as the number of layers of CFRP increases was (5.53%). Furthermore, increasing the number of CFRP layers of columns under (W) environment was studied, and the results showed that as the number of CFRP layers increased, this led to an increase in ultimate strength (12.70–22.31%) compared with the column (without CFRP).In addition, the use of CFRP shell led to enhancing the ultimate strength of the columns, ductility index, and stiffness significantly, so that it changed the failure mode for the better in comparison with the unstrengthen columns.