A process for purifying crude dicyclopentadiene which comprises the steps of: cracking the crude dicyclopentadiene to form a monomeric-containing effluent which comprises at least one monomer selected from the group consisting of: C.sub.4 acyclic dienes, C.sub.5 acyclic dienes, cyclopentadiene and methylcyclopentadiene; separating the monomeric-containing effluent into a cyclopentadiene-enriched stream and a cyclopentadiene-poor stream; dimerizing the cyclopentadiene-enriched stream to form a dimerizer effluent; contacting a membrane separator under pervaporation conditions with the dimerizer effluent wherein the C.sub.4 acyclic dienes, C.sub.5 acyclic dienes and cyclopentadiene permeate through the membrane separator and wherein a dicyclopentadiene product having a purity of at least about 98% is retained as retentate.