This study aims to investigate the effectiveness of strengthening perforated RHS stub columns using external doubler plates under axial static compressive load. The perforation was made as two opposing central circular openings at mid height of the column in the long sides of the RHS. The Finite element method was used to model the behavior of the strengthened stub columns. For comparison, perforated columns and imperforated columns were considered. The nonlinear geometry and nonlinear material effects were included in the model. The finite element model was verified against the experimental results obtained and presented by the authors in Reference [16]. A parametric study was performed considering 250 cases in order to investigate the effects of the RHS thickness, the opening diameter, and the doubler plate height and thickness on the axial strength of the strengthened perforated stub columns. The results were compared to the cases of counterpart perforated columns and columns without openings. The North American Specification AISI S100-16 (2016) was used to calculate the nominal compressive axial capacity of the column according to Section E of the specification. The results showed that using doubler plates for strengthening perforated stub columns of RHS upgraded the axial strength of the columns up to 40%. In some cases, the use of doubler plates overcame the effect of the openings and improved the axial strength of the column up to the value of a counterpart column without opening.