This paper describes the synthesis of telechelic polyisobutylene through the metathetical degradation of poly(isobutylene-co-butadiene) copolymer in the presence of a trialkylborane-containing acyclic olefin. Despite the relatively small amounts of butadiene units in the polymer chain, the degradation reaction proceeded fairly satisfactorily with a concomitant introduction of trialkylborane at the cleaved chain ends. The effects of various reaction times and acyclic olefin concentrations on the molecular weight of the final product were studied. The trialkylboranes thus obtained at the chain ends were quantitatively converted to the primary alcohol and iodo groups. The extent of functionalization at the chain ends was further evaluated by column chromatography and the synthesis of block copolymers of polycaprolactone and polyisobutylene.