The thermal transitions of a nylon 6/layered silicate nanocomposite were studied by differential scanning calorimetry and in-situ synchrotron X-ray diffraction. The drawn film of the nylon 6/layered silicate nanocomposite typically showed three endotherms in the DSC thermogram; a very broad endotherm at ~120°C (T1), a double-melting endotherm at ~215°C (T2), and a high temperature endotherm at ~240°C (T3). The drawn film of the nylon 6/layered silicate nanocomposite was comprised of a mixture of the α and γ forms, with the α form being generated by drawing the pressed film having the γ form. The melting and crystallization of the crystals were observed at the above thermal transitions during the heating experiment performed at the Pohang X-ray synchrotron radiation source (4C2). The newly generated form was meta-stable and melted at ~T1. The double-melting at ~T2 was due to the exothermic crystallization of the α form during the main endothermic melting of the γ form. The α form crystallized at ~T2 and melted at ~T3.