The title compound, 4-n-pentylphenyl-4'-n-butyloxythiobenzoate (4OS5), C22H28O2S, crystallized from methanol and hexane, reveals two polymorph forms in the crystalline state. The crystal and molecular structures of both polymorphs 4OS5-M (from methanol) and 4OS5-H (from hexane) are reported. 4OS5-M crystallizes in the monoclinic system, space group C2/c, with cell constants a = 39.43(2), b = 5.426(3), c = 20.392(5) Angstrom, beta = 105.15(3)degrees, V = 4211(3) Angstrom(3) , and Z = 8. The crystal data of 4OS5-H are: monoclinic system, space group P2(1)/c, a = 13.512(6), b = 8.427(2), c = 18.630(5) Angstrom, beta = 96.98(3)degrees, V = 2106(1) Angstrom(3), Z = 4. The structures were solved by direct methods and refined to the final R = 0.0569 and 0.0982 for 3242 and 1498 observed reflections for 4OS5-M and 4OS5-H, respectively. The molecules of both polymorphs 4OS5 differ only in the conformation of butyloxy chain: all trans in 4OS5-M and trans-gauche-trans in 4OS5-H. Theoretical calculations made by semiempirical AM1-MNDO method showed that both conformations are stable and almost equienergetical. The unit-cell packing in crystals of 4OS5 is characterized by the occurrence of the molecular layers, additionally stabilized by the net of weak C-H...O intermolecular hydrogen bonds in 4OS5-M.