The densities of tetra-n-butylphosphonium bromide in ethanol, 1-propanol, 1-butanol, acetone, and acetonitrile at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and sound velocities at 298.15 K have been measured. From these data, apparent molar volumes V(Phi) at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and the apparent molar isentropic compressibility K(S,Phi), at 298.15 K of tetrabutylphosphonium bromide in nonaqueous solvents have been determined.