Colorectal cancer (CRC) remains one of the leading causes of cancer-related mortality in the USA. As much as 50–60% of CRC patients develop resistance to 5-fluorouracil (5FU)-based chemotherapeutic regimens, attributing the increased overall morbidity and mortality. In view of the growing evidence that active principles in various naturally occurring botanicals can facilitate chemosensitization in cancer cells, herein, we undertook a comprehensive effort in interrogating the activity of one such botanical—andrographis—by analyzing its activity in CRC cell lines [both sensitive and 5FU resistant (5FUR)], a xenograft animal model and patient-derived tumor organoids. We observed that combined treatment with andrographis was synergistic and resulted in a significant and dose-dependent increase in the efficacy of 5FU in HCT116 and SW480 5FUR cells (P < 0.05), reduced clonogenic formation (P < 0.01) and increased rates of caspase-9-mediated apoptosis (P < 0.05). The genomewide expression analysis in cell lines led us to uncover that activation of ferroptosis and suppression of β-catenin/Wnt-signaling pathways were the key mediators for the anti-cancer and chemosensitizing effects of andrographis. Subsequently, we validated our findings in a xenograft animal model, as well as two independent CRC patient-derived organoids—which confirmed that combined treatment with andrographis was significantly more effective than 5FU and andrographis alone and that these effects were in part orchestrated through dysregulated expression of key genes (including HMOX1, GCLC, GCLM and TCF7L2) within the ferroptosis and Wnt-signaling pathways. Collectively, our data highlight that andrographis might offer a safe and inexpensive adjunctive therapeutic option in the management of CRC patients.