Flowers of angiosperms attract pollinators such as insects to transfer pollen to the stigmas of conspecific individuals, thereby ensuring reproductive success. In this mutualistic relationship, pollinators provide pollination services, while plants offer rewards such as nectar. This relationship has driven the coevolution of floral traits—including color, morphology, scent, nectar, and other traits—and pollinator preferences. Different pollinators exhibit specific preferences for these traits, and the suite of floral characteristics adapted to particular pollinators is collectively referred to as the pollination syndrome.When environmental conditions change or pollinators change, plants may undergo pollinator shifts to adapt to new pollinators. Evidence from multiple plant families and genera suggests that such shifts not only drive innovations in floral traits but also promote population divergence through pollinator-mediated reproductive isolation, ultimately serving as a key mechanism for rapid species radiation in angiosperms. However, the molecular mechanisms by which pollinator shifts drive speciation remain unclear. Advances in genomics and molecular genetics have accelerated the identification of key genes, enhancing our understanding of pollinator-mediated reproductive isolation. In this review, we first introduce the concepts of pollination syndromes and pollinator shifts, then highlight recent progress in elucidating the molecular mechanisms underlying the transition of pollination syndromes. Finally, we discuss the interactions between pollinator-mediated reproductive isolation and other isolation mechanisms, as well as their implications for the process of speciation.