Objective: VEGF-C has recently been identified as a key molecule which is involved in tumor lymphangiogenesis. The aim of this research was to investigate the role of PARP-1 inhibition in the regulation of VEGF-C expression in CT26 cells. Methods: CT26 cells were treated with or without the PARP-1 inhibitor 5-aminoisoquinolinone (5-AIQ). The expression of PARP-1, NF-kB, and VEGF-C proteins in CT26 cells was measured by Western blot analysis and the VEGF-C mRNA level was determined by reverse transcription polymerase chain reaction (RT-PCR). CT26-secreted VEGF-C was detected by enzyme-linked immunosorbent assay (ELISA). Results: The results of Western blot analysis showed that the expression levels of PARP-1, NF-kB, and VEGF-C were reduced in 5-AIQ treated CT26 cells and the levels of VEGF-C mRNA in 5-AIQ treated CT26 were significantly lower than t in 5-AIQ-untreated cells (P<0.05). The concentrations of CT26-secreted VEGF-C were also dramatically decreased (P<0.05). Conclusion: Here, we provide evidence for the first time that PARP-1 inhibition dramatically reduces VEGF-C expression via the nuclear factor NF-kB signaling pathway. We therefore propose that PARP-1 inhibition has an anti-lymphangiogenic effect and may contribute to the prevention of metastatic dissemination via the lymphatic system.