We report the synthesis and characterization of poly(3-decylselenylene vinylene) (P3DSV) homopolymers and poly(3-decylselenylene vinylene)-co-poly(3-decylthienylene vinylene) (P3DSV-co-P3DTV) copolymers through acyclic diene metathesis (ADMET) polymerization techniques. The obtained polymers were fully characterized. P3DSV was found to possess reduced crystallinity and a smaller bandgap of about 1.6 eV, compared with those of poly(3-decylthienylene vinylene) (P3DTV) analogs. P3DSV-co-P3DTV shows electronic properties between those of the corresponding homopolymers and distinctly different from those of simple blends of the two homopolymers. Our methodology provides a new way to control the physical and electronic properties of low bandgap poly(arylene vinylene)s (PAVs).