Expression of sphingosine kinase 1 (SPHK1) plays a role in colorectal cancer progression. This study aimed to demonstrate the mechanism of human colorectal cancer cell metastatic phenotype through SPHK1 knockdown. Human colorectal cancer HT-29 cells were stimulated by phorbol 12-myristate 13-acetate (PMA) with or without SPHK1 siRNA transfection. Tumor cell phenotypic changes were analyzed by using invasion, motility, cell viability, and apoptosis assays. Gene expressions were assessed using Western blot. PMA induced a metastatic phenotype in colorectal cancer cells, as indicated by cell viability, migration and invasion capacity, and ERK1/2 phosphorylation, whereas SPHK1 siRNA transfection suppressed the metastatic phenotype of tumor cells and antagonized PMA's effects. SPHK1 knockdown also inhibited secretion of MMP-2 and MMP-9 into the tumor cell conditioned medium. Suppression of SPHK1 expression suppresses the PMA-induced metastatic phenotype via ERK1/2 phosphorylation in human colorectal cancer cells.