Here we report the synthesis of novel poly(3-alkyl-2,5-selenylenevinylene)s (PSV) by the polymerization of 2,5-dibromo-3-alkylselenophene and (E)-1,2-bis(tributylstannyl)ethylene under microwave-assisted Stille coupling conditions. Polymers containing hexyl and decyl side chains were prepared. The decyl-substituted polymer exhibited good solubility in common organic solvents, and 1H NMR analysis indicated a side-chain regioregularity in excess of 90%. The polymer exhibits an absorption maxima at 621 nm in solution, with a significant red shift in absorption upon film formation. Thin film transistors fabricated from PSV exhibited hole carrier mobilities up to 0.01 cm2/(V s). The polymer displayed balanced ambipolar performance when hydroxyl free organic dielectrics were used as the gate insulator.