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Materials research has shown geopolymer concrete has the potential to significantly improve the sustainability of concrete construction. In this study, the structural performance of geopolymer concrete-filled steel tube members to take advantage of the beneficial confinement from the outer steel tubes is investigated experimentally and numerically. Experiments on eleven geopolymer concrete-filled steel tube specimens with either square or circular sections subjected to compression, flexure or combined loading conditions are presented. The experimental results, including the ultimate strength, load-deformation responses and failure modes, are obtained and also used as the basis for the validation of a finite element model which is subsequently used to perform parametric studies on the structures with varying cross-sectional dimensions, steel yield strength and member slenderness ratios. The experimental and numerical results are also used to evaluate the applicability of existing design standards for geopolymer concrete-filled steel tube members under combined compression and bending. The evaluation shows that the design approaches developed for ordinary Portland concrete-filled steel tubes in existing standards provide conservative strength predictions for the structures with the geopolymer concrete infill and can therefore be directly applied for safe structural design. [Display omitted] • Geopolymer-concrete-filled steel tube members under combined loading were examined. • Experiments and numerical modelling on the structures were performed. • The applicability of existing design approaches was assessed and discussed. • The existing design approaches can be applied to generate safe structural design. [ABSTRACT FROM AUTHOR]