Martensite morphology such as connectivity or dispersivity in ferrite (F)/martensite (M) dual-phase (DP) steels was investigated from topological viewpoint to reveal the effect of the martensite morphology on the mechanical properties. Topological analysis permits evaluation of the microstructural connectivity and dispersivity by measuring the number of handles, independent bodies and genus, etc. The topological analysis was performed on three-dimensional (3D) reconstructed images of the microstructure with different connectivity, dispersivity, volume fraction and hardness of martensite in DP steels that were prepared by changing the intercritical annealing temperature. The connectivity and the volume fraction of martensite increased while the dispersivity and hardness of it decreased with increasing annealing temperature. The effect of connectivity and dispersivity as well as volume fraction and hardness, in particular, on work hardening behavior was individually evaluated at a given strain.