A piezoelectric resonator component includes an energy-trapped piezoelectric resonator utilizing a third order harmonic wave of thickness longitudinal vibration and including a piezoelectric substrate having first and second major surfaces and polarized in a direction of thickness between the first and second major surfaces, and first and second vibrating electrodes opposed to each other with thepiezoelectric substrate interposed therebetween, and first and second casing substrates respectively laminated on the first and second major surfaces of the piezoelectric resonator so that cavities are arranged so as not to interfere with vibration of a vibration section where the first and second vibrating electrodes face each other through the piezoelectric substrate. The first and second vibrating electrodes are dimensioned so that the difference between the peak values of the phases of S0 and S1 modes of the fundamental wave of the thickness longitudinal vibration falls within a range of about +/-5 degrees.