Polo-Like Kinase 1 (PLK1), a serine/threonine kinase involved in cell cycle regulation at the G2/M transition, is associated with high-risk neuroblastoma (NB) and unfavorable patient outcome. Recently, we and others demonstrated that PLK1 is a potential drug target in neuroblastoma and reported antitumoral actvity of the PLK1 inhibitor BI2536 in preclinical models of NB. We here analyzed the effects of the ATP-competitive PLK1 inhibitor GSK461364 on typical tumorigenic properties of preclinical in vitro and in vivo models of NB. Treatment of NB cells with GSK461364 resulted in decreased cell viability and reduction of proliferative capacity, and led to cell cycle arrest and massive induction of apoptosis. These phenotypic consequences were observed at low-dose nanomolar levels and were independent of the MYCN copy number status of the cell lines. In vivo treatment with GSK461364 led to a strong delay in tumor development and to a highly significant increase in survival in the treatment group. These preclinical findings highlight the promise of PLK1 inhibitors as novel agents for NB and serve as rationale to move forward with early phase clinical trials in children.