This work investigates the use of a zeolite membrane reactor (ZMR) in the liquid-phase oligomerization of i-butene. The membrane was used for the selective removal of i-octene from the reaction environment, thus reducing the formation of unwanted C-12 and C-16 hydrocarbons. MFI (silicalite) membranes prepared by secondary growth on stainless steel porous tubes were used for this purpose, given the non-polar nature of the compounds to be separated. Preliminary non-reactive tests demonstrated the capability of the membrane to separate i-octene from i-butene and from C-12 and C-16 hydrocarbons. Reaction experiments were then carried out over an acid resin catalyst bed located on the membrane tube side. The ZMR produced a very significant increase in the selectivity, and as a consequence also in the yield of i-octenes (intermediate product in the oligomerization of i-butene), compared to a conventional fixed bed reactor (FBR).