Suberoylanilide hydroxamic acid (SAHA), a potent histone deacetylase (HDAC) inhibitor, has been shown to exert anticancer effects in various types of human cancer and is now used in the clinic for cancer treatment. In addition to cytostatic and cytotoxic activities, SAHA also represses angiogenesis to inhibit tumor growth. However, the effect of SAHA on tumor lymphangiogenesis, a step in which cancer cells produce pro-lymphangiogenic factors such as vascular endothelial growth factor-C (VEGF-C) to stimulate proliferation and migration of lymphatic endothelial cells, remains largely unclear. In this study, we investigated the expression of VEGF-C in breast cancer cell lines and found that VEGF-C was highly expressed in MDA-MB-231, MCF-7, MDA-MB-453 and BT-474 cells. SAHA inhibited VEGF-C expression in a dose-dependent manner in these cell lines. The secretion of VEGF-C into conditioned medium was also suppressed. We cloned human VEGF-C gene promoter and demonstrated that SAHA directly repressed promoter activity in MDA-MB-231 cells. Promoter deletion assay suggested that SAHA repressed VEGF-C via the -185/+38 region which contained several transcription factor binding sites. Notably, we found that SAHA reduced Sp1, but not Sp3 and NF-κB protein levels. Treatment with Sp1 inhibitor mithramycin A also inhibited VEGF-C expression in breast cancer cells. In addition, enforced expression of Sp1 partially rescued the inhibition of VEGF-C by SAHA. Collectively, our results suggest that SAHA inhibits VEGF-C expression in breast cancer cells via transcriptional repression and this drug may exert anti-lymphangiogenic activity in cancer treatment.