Abstract In order to determine the enthalpy change in an irreversible field-induced phase transition, the thermal response to an electric field in 0.87Pb(Mg₁/₃Nb₂/₃)O₃-0.13PbTiO₃ was measured and dismantled into characteristic dielectric hysteresis, reversible electrocaloric, and irreversible phase transition responses. Below the depolarization temperature Tdp = 18 °C, the phase transition enthalpy change increases rapidly to a maximum value of |ΔH| = 77 J / kg. Above Tdp, the field-induced thermal response shows a reversible nature with an increased electrocaloric effect. In addition to earlier enthalpy data presented for temperature-induced transitions, this letter provides information on the enthalpy change in a field-induced phase transition of relaxor ferroelectrics.