Disclosed is a thermoplastic elastomer composition including a thermoplastic elastomer (A) having a side chain having at least one member selected from the group consisting of imino group, nitrogen-containing heterocycle and covalent crosslink site, and a carbonyl-containing group, and an ethylene-propylene copolymer (B) comprising propylene block and ethylene-propylene block. The thermoplastic elastomer of the present invention exhibits excellent high temperature flowability and mechanical strength while retaining its excellent flexibility.