Abstract This paper presents a one-dimensional finite element analysis of tapered thin-walled box beams under out-of-plane loads and twisting moments by developing new C 0 -continuous tapered higher-order beam elements. While higher-order sectional deformations such as distortion were considered earlier, there was no theoretical or finite element analysis on the tapering effect of variable cross-sectioned box beams. Case studies considering tapered box beams with various height-to-width ratios and a system of joint structure with a tapered box beam show that the results by the developed method are comparable with the shell finite element results unlike the stepped Timoshenko beam element results.