To provide a resin composition including: an ethylene-vinyl alcohol copolymer (A) having an ethylene content of from 15 to 65 mol % and a saponification degree of at least 95 mol %, a phosphoric acid salt (B) which can form a hydrate, and a conjugated polyene compound (C) having a boiling point of at least 150.degree. C., wherein the resin composition comprises from 50 to 99 parts by weight of (A), from 1 to 50 parts by weight of (B) and from 0.00001 to 1 parts by weight of (C), based on 100 parts by weight of the total amounts of (A) and (B). This resin composition excels in gas barrier property and also in moisture resistance at high temperatures and high humidities. Therefore, it is suitable for food packaging containers to be retorted.