cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki−Miyaura coupling of arylboronic acids with (Z)-bromoalkenes in over 96% geometrical purity. On the other hand, trans-oligo(phenylenevinylene)s can be synthesized by Hiyama coupling of aryl iodide with (E)-alkenylsilanes in almost perfect purities. Effect of π-conjugation chain length on photoisomerization behavior of OPVs is described.