Two series of heteroleptic cyclometalated platinum(II) complexes [(C(n)Oppy)Pt(acac) and (C(n)OFppy)Pt(acac)] have been prepared. Their liquid-crystal and optophysical properties were studied, in which C(n)Oppy is 2-(4-alkoxyphenyl)-5-(alkoxymethyl)pyridine and C(n)OFppy is 2-(3-fluoro-4-alkoxyphenyl)-5-(alkoxymethyl)pyridine. Only the heteroleptic cyclometalated platinum(II) complexes (n = 12 and 16) exhibited enantiotropic mesophase transitions with smectic (S(m)) structure. Intense polarized luminescence with a maximum peak at 532 nm and a polarization ratio as high as 10.5 were obtained in an aligned polyimide film under opto-excitation at room temperature. This research work provides a simple approach to realize high-efficiency polarized emission by heteroleptic cyclometalated platinum(II) complexes.