Introduction and Aims: CFTR, a transmembrane Cl- channel important in regulating intestinal fluid and electrolyte secretion, is implicated in the pathogenesis of a number of intestinal disorders. Bile acids, classically known for their roles in lipid digestion, are now also recognised as important enteric hormones that regulate many aspects of epithelial function. Previous studies from our laboratory have shown that, at physiological concentrations, bile acids, acting via the nuclear receptor, farnesoid x receptor (FXR), inhibit colonic epithelial CFTR expression. Dietary phytochemicals have been reported to have the capacity to modulate FXR signalling. Here, we set out to investigate mechanisms underlying FXR regulation of epithelial CFTR expression, and the potential for therapeutically targeting the receptor with dietary phytochemicals.   Methods: T84 colonic epithelial cells were cultured as monolayers on permeable supports and treated with the FXR agonist, GW4064 (5 µM), in the absence or presence of the plant phytochemical, designated here as KFS1 (5 µM). Expression of CFTR and FXR were measured by qRT-PCR and immunoblotting. Expression of NF-κB, FOXA1, HNF1A, and CDX2, transcription factors thought to be involved in the regulation of CFTR expression, were also measured by qRT-PCR. Nuclear translocation of NF-κB was measured by immunoblotting. Electrophysiological studies of T84 cells were conducted in Ussing chambers.   Results: Treatment of T84 monolayers with GW4064 significantly downregulated CFTR mRNA to 0.51 ± 0.06 fold after 12 hrs (n = 12; p < 0.001) and protein levels to 0.28 ± 0.0 6 fold after 48 hrs, compared to controls (n = 8; p < 0.001). Electrophysiological studies in Ussing chambers showed that GW4064 treatment for 48 hrs inhibited Cl- secretory responses to the Ca2+-dependent agonist carbachol (CCh; 100 mM) and the cAMP-dependent agonist, forskolin (FSK; 10 mM)  by 79.9 ± 7.5 % and 74.2 ± 8.9 %, respectively. Transcriptomic analysis of human colonic enteroids revealed FXR to be robustly expressed in secretory (crypt-like) cells, that its levels were inversely correlated with those of CFTR, and that its activation also induced CFTR downregulation. FXR activation did not alter the expression or phosphorylation of the p65 subunit of NF-κB, or inhibit its translocation to the nucleus. GW4064 downregulated FOXA1 mRNA expression by 33.2 ± 5.2% after 3 hrs (n = 4; p < 0.05), but had no effect on HNF1A or CDX2 expression. Treatment with the phytochemical, KFS1 (5 mM; 24hrs), upregulated FXR mRNA and protein expression in T84 cells and enhanced GW4064-induced downregulation of CFTR mRNA by 0.28 ± 0.05 fold (n = 8; p < 0.01) and protein by 0.25 ± 0.11 fold (n = 4) after 24 hours. KFS1 also enhanced FXR downregulation of Cl- secretory responses in Ussing chambers.   Conclusion: The nuclear bile acid receptor, FXR, regulates colonic epithelial CFTR expression and function by a mechanism which appears independent of NF-κB, but which may involve FOXA1. By virtue of their ability to upregulate FXR expression, and thereby enhance its antisecretory actions, plant extracts containing KFS1 have excellent potential to be developed as targeted nutraceuticals for the treatment and prevention intestinal disease.