In this paper an experimental and numerical investigations were performed to study the performance of partially jacketed R.C. columns subjected to both axial and lateral loads. The current research also investigates the effect of the lateral load direction, with respect to jacket's direction during constant axial load, on the structural response of strengthened columns. The experimental study consists of seven square columns of 100 x 100 mm2 cross-section dimensions and total length of 1000 mm. The columns were strengthened from different sides with 50 mm concrete jackets. The strengthened columns were tested under constant axial load with an increasing lateral force up to column failure. Columns capacities and modes of failure were illustrated and discussed. Going deep into the investigation, a finite element analysis was performed on the experimented columns. A satisfactory agreement was found when the experimental and numerical data were compared together. The ultimate lateral loads of the strengthened columns from two, three, and four sides increased up to 5.83, 8.43, and 11.03 times the lateral load capacity of control columns, respectively. The study also concluded that the loading direction has a significant effect on column lateral capacity.