ABSTRACT This article deals with the effect of voids, magnetic field and rotation on the reflection of P waves in thermoelastic medium under the purview of three-phase-lag model. The basic governing equations for isotropic and homogeneous thermoelastic half-space with voids and rotation in the presence of a magnetic field are presented. The solution of the problem in plane indicates the existence of four plane waves: and and SV waves. The relevant boundary conditions at stress-free thermally insulated surface are satisfied by appropriate solutions in the half-space to obtain the reflection coefficients for the incidence of P waves. The numerical values of the complex modulus of the reflection coefficients are presented graphically to show the effect of rotation, magnetic field and phase lag.