A simultaneous analysis of the ³⁵Cl NQR transition frequency and of the molar heat capacity temperature dependences has been carried out for solid methyl chloride. The values for the various deduced quantities (Debye frequency, effective rotary mode frequency, etc.) are found to be very reasonable and produce an excellent description of the data, therefore giving the authors confidence in the models and method employed. The NQR transition frequency shows a thermal activated process which is assigned to the hindered rotations of the methyl group.