Ulcerative colitis (UC) is a chronic inflammatory bowel disease. The etiology of UC is multifaceted, and the underlying pathogenesis remains incompletely understood. Pyroptosis, programmed cell death mediated by the gasdermins, is a pivotal driver of UC pathology due to its dual role in epithelial barrier disruption and inflammatory amplification. We previously showed that phenethyl isothiocyanate (PEITC), an isothiocyanate derived from cruciferous vegetables, alleviated acute liver injury in mice by suppressing hepatocyte pyroptosis. In this study we evaluated the therapeutic potential of PEITC in the treatment of UC and the underlying mechanisms. UC mouse models were established by administration of 2.5% (w/v) dextran sulfate sodium (DSS) daily for 7 days. PEITC (5, 10, or 20 mg·kg·d, i.g.) was given 2 days before the start of modeling, and the dosing lasted for a total of 10 days. We showed that during the progression of DSS-induced UC, the pyroptosis pathway was activated accompanied by elevated expression levels of thioredoxin-interacting protein (TXNIP) and NOD-like receptor thermal protein domain associated protein 3 (NLRP3), as well as the activation of caspase-1, gasdermin D (GSDMD) and interleukin-1β (IL-1β). Treatment with PEITC dose-dependently reduced TXNIP and NLRP3 expression while inhibiting the cleavage of proteins associated with the pyroptosis pathway such as caspase-1, GSDMD, and IL-1β. We confirmed the inhibitory effect of PEITC on colonocyte pyroptosis in an in vitro model established in HT29 cells, where PEITC (0.2, 1, 5 µM) dose-dependently inhibited TXNIP and NLRP3 expression and the activation of pro-caspase-1, GSDMD and pro-IL-1β. We revealed that PEITC is directly bound to TXNIP and disrupted the interaction between TXNIP and NLRP3, leading to diminished cellular inflammation and oxidative stress levels. In conclusion, this study demonstrates that PEITC disrupts the interaction of TXNIP and NLRP3 by binding to TXNIP, inhibits NLRP3 activation and colonocyte pyroptosis, and thus effectively alleviates UC symptoms in mice. This study offers novel drug targets along with potential therapeutic candidates for the clinical prevention and treatment of UC.