Corrosion of steel bars in reinforced concrete (RC) due to environmental exposure results in service life and durability reduction and subsequent premature failure of structures. Columns are considered as critical components of a structure. Partial or full loss of columns' steel reinforcement due to corrosion can potentially lead to the collapse of the entire structure. An effective retrofit procedure is required to restore the performance of these damaged columns. The present numerical study investigates the use of near-surface mounted (NSM) CFRP rods as a retrofit technique for eccentrically loaded slender columns that partially or fully have lost their internal steel reinforcement due to corrosive environment. The proposed numerical model is corroborated with experimental results available in the literature. A parametric study was conducted to study the effectiveness of the NSM CFRP rods retrofitting to structurally compensate for the lost corroded steel reinforcement of as-built columns for ten different scenarios. The performance of retrofitted columns was assessed through axial load versus moment response plots. The results indicate that the NSM CFRP rods were able to regain the reduction in strength caused by the loss of internal steel reinforcement of damaged columns. Whereas in some scenarios, axial load and moment carrying capacities were increased.