Colorectal cancer (CRC) is considered one of the leading types of cancer in the world. CD133, as a cancer stem cell marker, has a pivotal role in the development of drug resistance, migration, and stemness properties of CRC cells. This study was designed to check the combined effect of CD133 siRNA and Oxaliplatin on proliferation, migration, apoptosis, and stemness properties of CRC cells in the HT-29 cell line. MTT assay was performed to define the combined effect of CD133 siRNA and Oxaliplatin on the viability of HT-29 cells, and it showed that the combination of CD133 siRNA and Oxaliplatin could reduce the IC50 of this drug from 32.85 to 19.75 nmol. In order to figure out the effect of this combination therapy on CD133 expression at the gene and protein level, qRT-PCR and western blot were exploited, respectively. The results demonstrated that the silencing of CD133 could reduce the relative expression of this marker to about 0.00001 compared to the control group and reduce the protein level to 0.01. The ability of cell migration was tested by wound healing assay as well. Also, colony formation and sphere formation were conducted to assess the stemness properties in the combination group. Flow cytometry was conducted to investigate the apoptosis (15%), cell cycle (about 10% arresting in G0-G1 phase), and surface expression of CD133 in different groups (from 39.3% in the control group to 2.41 in the combination group). Finally, the expression of migration-, and stemness-associated genes were measured by qRT-PCR. We indicated that silencing of CD133 reduces the migration and stemness properties of colorectal cancerous cells. This suppression makes HT-29 cells more sensitive to Oxaliplatin and reduces the effective dose of this chemical drug. Therefore, the suppression of CD133 in combination with Oxaliplatin treatment might be a promising therapeutic approach in the treatment of colorectal cancer.