This paper reports an experimental study about the pressure dependence of the vibrational modes of tricosane paraffin (C23H48) investigated by in situ Raman and infrared spectroscopy in a diamond anvil cell (DAC). The main vibrational bands were followed up to 11GPa and the observed behavior indicated a conformational disorder induced by pressure, corresponding to a transition from ordered to disordered state of the linear chains from 2 to 5GPa followed by a transition to an amorphous state under pressure above 5GPa. However, this behavior was reversible after compression–decompression cycle showing that this linear compound was structurally and chemically stable up to 11GPa at room temperature.