Background: Therapeutic approaches to gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are still not satisfactory. A new direction in treatment options could be the novel aurora kinase inhibitor ZM447439, which was previously reported to interfere with the mitotic spindle integrity checkpoint and chromosome segregation, but does not interfere with other kinases when used up to 5 µM. Methods: We evaluated the antineoplastic effects of ZM447439 on growth and apoptosis of the GEP-NET cell lines BON, QGP-1 and MIP-101, representing the different malignant tumor types, using standard cell biological tests as crystal violet assays, caspase activation, DNA fragmentation and cell cycle analysis. Results: ZM447439 dose-dependently inhibited proliferation of all three cell lines with IC₅₀ values in the nanomolar to low micromolar range. Moreover, aurora kinase inhibition by ZM447439 potently induced apoptosis, which was accompanied by DNA fragmentation and caspase 3 and 7 activation. Furthermore, we observed cell cycle arrest at G₀/G₁ phase as well as a block in G₂/M transition. In addition, combined treatment with the chemotherapeutic agents streptozocin and cisplatin augmented significantly the antiproliferative effects of those agents. Conclusion: Aurora kinase inhibition by ZM447439 seems to be a promising new therapeutic approach in GEP-NETs, which should be evaluated in further clinical trials.