A total of 270 nonlinear steady-state finite element (FE) analyses were performed on 54 FE models of two-planar CHS KK-joints subjected to axial loading at five different temperatures (20°C, 200°C, 400°C, 550°C, and 700°C). The main objective was to study the influence of temperature and dimensionless geometrical parameters on the ultimate load, failure modes, and initial stiffness of the KK-joints. Results indicated that on an average basis, the ultimate load of a two-planar tubular KK-joint at 200°C, 400°C, 550°C, and 700°C is 90%, 75%, 45%, and 16% of the joint’s ultimate load at ambient temperature, respectively. Outcomes of the parametric study showed that replacing the yield stress at ambient temperature with the corresponding value at elevated temperature, to apply the EN 1993-1-8 equations for the calculation of the joint’s ultimate load at elevated temperatures, may lead to highly unconservative results that might endanger the safety of the structure. Results of the parametric study were then used to develop a set of design formulas, through nonlinear regression analyses, to calculate the ultimate load of two-planar tubular KK-joints subjected to axial loading at elevated temperatures.