Background: Overexpression of the angiotensin-II receptor and renin–angiotensin system (RAS) has been reported in several malignancies, including colorectal-cancer (CRC), indicating its potential value as a therapeutic target. Here we explored the impact of targeting the RAS using an angiotensin II receptor blocker, valsartan, alone and its combination with Fluorouracil (5-FU) in in vitro and in vivo models of CRC. Methods: Anti-proliferative activity of valsartan was evaluated in 2−/3-dimensional in vitro and in vivo CRC mouse models. The anti-migratory effects of this agent was assessed by wound-healing assay, while apoptosis was studied using 4′,6-diamidino-2-phenylindole or DAPI staining, and staining with Annexin-V–fluorescein isothiocyanate with analysis using FACS. Gene-expression was determined at mRNA and protein levels. We further evaluated the anti-inflammatory properties of valsartan by histological analysis and the measurement of oxidative/antioxidant markers. Gelatin zymography was used to measure matrix metalloproteinase-2 and -9 activity (MMP-2 and 9). Results: Valsartan suppressed CRC cell-growth and synergistically enhanced the anti-tumor-activities of 5-FU by induction of apoptosis, BAX, BCL2, P53 and modulation of the cell cycle. Valsartan inhibited the cell migration by perturbation of MMP2/9. Furthermore, valsartan inhibited tumor-growth, and this was more pronounced when using the valsartan/5-FU combination. The plausible mechanism for this is via the induction of ROS and down-regulation of SOD, thiol/catalase as well as VEGF. Valsartan may protect cells against intestinal fibrosis by modulation of pro-fibrotic and pro-inflammatory factors including interleukins and Col1A1 expression. Conclusions: Our findings demonstrated that targeting RAS pathway using Valsartan interferes with cell-proliferation, induces apoptosis, reduces migration and synergistically interacts with 5-FU, supporting further studies on this new therapeutic approach for colorectal cancer.