Reinforced concrete (RC) columns are the backbone of RC buildings, essential for supporting the structure's weight. If an RC column is not designed to carry the expected live loads, it may be necessary to strengthen it. One of the most effective methods for strengthening RC columns is steel jackets. This research conducted a numerical investigation of the effect of strengthening RC columns with a steel jacket on the axial load capacity. The steel jacket consisting of two C-channels connected with various numbers of welded batten plates was adopted. The finite element (FE) analysis of 7 columns was conducted using Abaqus/CAE software. All the columns have a cross-section of 300 x 300 mm with a 2500 mm height and are reinforced with four longitudinal bars of 16 mm diameter with five stirrups per meter of 8 mm diameter. The strengthened col-umns were divided into two groups. The first group consisted of four strength-ened columns; the two C-channels connected with 2, 3, 5, and 7 batten plates from both sides. The second group consisted of two strengthened columns; the two C-channels connected with one large plate. The results showed that using two C-channels as a steel jacket is very effective as a relatively rigid jacket can increase the failure load of the columns by a minimum value of 21.46 %. Also, the more batten plates connecting the two C-channels steel jackets, the more confinement of the column and, hence, the more the column failure load in-creases. Moreover, connecting the two C-channels steel jacket by a single large plate to form a complete box around the column gives the best confinement and could increase the failure of the column by 75.92 %.