We investigated the mechanism of strong thermal adhesive properties occurring between thermoplastic polyamide elastomers (PAE) and other polymers, for examples, thermoplastic polyurethanes (TPU) and cross-linked polybutadienes (cBR). The number-average radii of dispersed phases for PAE/TPU and PAE/BR blends prepared by melt-blending are so small. These results show that the interfacial tensions between PAE and TPU(BR) are small. In addition, the rheological behaviors of these blends in the molten state were also measured. Analyses of the long-time relaxation behaviors derived from the existence of the dispersed phases in blends resulted in small interfacial tensions between component polymers. We estimated that the small interfacial tensions between PAE and TPU(BR) bring the thick interfacial layers between them and the strong thermal adhesive properties between PAE and TPU(BR) are occurred by the thick interfacial layers due to the small interfacial tensions.