The work-hardening mechanisms of the Ti60Cu14Ni12Sn4Nb10 nanocomposite alloy were studied. This material is composed of micrometer-sized dendrites embedded in a nanostructured eutectic matrix and a CuTi2 intermetallic phase. Our study shows that, in the as-quenched state, the nanostructured eutectic matrix behaves softer than the dendrites. During mechanical deformation, both the dendrites and the eutectic matrix harden, whereas the hardness of the CuTi2 intermetallic phase remains unaltered. The high strength of the dendrites is caused by the interplay between solid solution hardening and dislocation networks during plastic flow. Interestingly, the mechanical hardening of the nanoeutectic matrix is also assisted by a martensitic transformation of the NiTi phase. Transmission electron microscopy studies clearly show that the martensitic transformation of this phase is accompanied with grain size refinement, which also plays a role in the deformation-induced mechanical hardening.