• Triaxial behavior of microcapsule-based concrete was investigated. • The effect of microcapsules on triaxial strength declined with confinement pressure. • Microcapsules improved the plastic capacity and post-peak bulk modulus of concrete. • Concrete behavior under large axial strain was controlled by granular skeletons. To promote the application of microcapsule-based self-healing concrete in engineering structures, it is important to study the mechanical behaviour under complex stress conditions. Accordingly, this study aims to investigate the mechanical behaviour of microcapsule-based self-healing concrete under the triaxial compression state with large axial strain. The self-healing concrete was prepared by mixing different dosages of UF/Epoxy microcapsules, and the influence of confinement pressure, large axial strain, and microcapsule dosage on the mechanical behaviour of concrete was investigated through uniaxial compression, conventional triaxial compression, and mercury intrusion porosimetry (MIP) test. The results show that incorporating microcapsules reduced the cohesive strength and internal friction angle of the concrete. In contrast, the influence of microcapsule dosage on triaxial strength was rapidly weakened with increasing confinement pressure. Both the incorporation of microcapsules and the application of confinement pressure can improve the plastic deformation capacity and reduce the brittleness of the specimens. In addition, microcapsules may increase the bulk modulus of the specimens in the hardening stage. It should be noted that under the action of triaxial loading with large axial strain, the ultimate strengths of specimens with different microcapsule dosages are similar, and concrete behaviour is mainly controlled by the granular skeleton.