Room-temperature Raman scattering and x-ray diffraction measurements together with first-principles calculations were employed to investigate the behavior of disordered Pb(In[Formula: see text]Nb[Formula: see text]O3 (PIN) under pressure up to 50[Formula: see text]GPa. Raman spectra show broad bands but a peak near the 380[Formula: see text]cm[Formula: see text] increases its intensity with pressure. The linewidth of the band at 550[Formula: see text]cm[Formula: see text] also increases with pressure, while two of the Raman peaks merge above 6[Formula: see text]GPa. Above 16[Formula: see text]GPa, we observe additional splitting of the band at 50[Formula: see text]cm[Formula: see text]. The pressure evolution of the diffraction patterns for PIN shows obvious Bragg peaks splitting above 16[Formula: see text]GPa; consistent with a symmetry lowering transition. The transition at 0.5[Formula: see text]GPa is identified as a pseudo-cubic to orthorhombic (Pbam) structural change whereas the transition at 16[Formula: see text]GPa is isostructure and associated with changes in linear compressibility and octahedral titling, and the transition at 30[Formula: see text]GPa is associated to an orthorhombic to monoclinic change. First-principles calculations indicate that the Pbam structure is ground state with antiferrodisdortion consistent with experiment.