Field-induced phase transitions in [111]- and [110]-oriented relaxor ferroelectric (1 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals in the morphotropic phase boundary (MPB) composition range were examined through temperature-dependent complex capacitance measurements. Two first-order phase transitions from paraelectric cubic to ferroelectric tetragonal and then to ferroelectric rhombohedral phases were observed in the unpoled crystal. Additional weak dielectric anomalies were observed at a temperature of ~ 40 °C (in both crystals) and ~ 90 °C (in [110] crystals) in the poled samples. These weak anomalies disappeared when cooling the crystal from higher temperature but within the ferroelectric tetragonal phase. The new anomalies were attributed to the formation of field-induced metastable phases, which were unstable with temperature modulation.