Provided is a thermoplastic elastomer composition, which includes a halogenated isoolefin/para-alkylstyrene copolymer rubber dispersed in a polyamide resin in order to improve the fatigue durability of a polyamide resin, while maintaining high flowability of the polyamide. A thermoplastic elastomer composition comprising a continuous phase composed of a modified polyamide resin (A) and a dispersed phase composed of a halogenated isoolefin/para-alkylstyrene copolymer rubber (B) is provided. The modified polyamide resin (A) is a resin obtained by melt-kneading 100 parts by weight of a polyamide resin (C) with not less than 0.05 part by weight and less than 3 parts by weight a compound (D), such as a monofunctional epoxy compound, capable of binding to a terminal amino group of the polyamide resin at a temperature not lower than the melting point of the polyamide resin (C). The composition can be used as an inner liner of a pneumatic tire.