A process for producing ethylbenzene is described in which benzene and ethylene are supplied to an alkylation reaction zone. Also added to the alkylation reaction zone is a C3+ olefin in an amount ofat least 200 ppm by weight of the ethylene supplied to the alkylation reaction zone. The benzene, ethylene and C3+ olefin are contacted with an alkylation catalyst in the alkylation reaction zone to alkylate at least part of the benzene and produce an alkylation effluent comprising ethylbenzene, polyethylated benzene and at least one mono-C3+ alkyl benzene. The alkylation effluent is separated into a first product fraction comprising ethylbenzene and a second fraction comprising polyethylated benzene and the at least one mono-C3+ alkyl benzene. The second fraction is then contacted with benzene in the presence of a transalkylation catalyst to convert at least part of the polyethylated benzene to ethylbenzene and produce a transalkylation effluent.