In adaptive radiation, a single species evolves into many ecologically diverse species in short term. It has been suggested that some adaptive radiations might have been triggered by hybridization between different lineages within a species, or between related species. Hybridization can facilitate rapid ecological adaptation and speciation by producing various novel genotypes in which genes from different parental lineages are assembled. However, it has also been argued that hybridization can inhibit speciation by breaking down genetic differentiation between incipient species. Thus, the role of hybridization in causing adaptive radiation is currently unclear. Here, we theoretically explore the conditions in which hybridization promotes adaptive radiation. We developed an individual-based model to simulate adaptive radiation that occurs in a hybrid zone between two lineages which have been geographically isolated for tens of thousands years. Simulation results suggested that hybridization can promote adaptive radiation in some conditions. Important factors determining whether hybridization led to adaptive radiation were (i) the level of genetic differentiation between parental lineages and (ii) the mechanism by which premating isolation develops between species.