Interstitial cystitis/bladder pain syndrome (IC/BPS) causes significant discomfort in patients and impairs the quality of urination. Pterostilbene (PTE), a natural polyphenol antioxidant, has demonstrated beneficial effects in mitigating inflammation, enhancing antioxidant capacity, and ameliorating organ dysfunction in various chronic nonspecific inflammatory conditions. The aim of this study was to evaluate the efficacy of PTE in IC/BPS and elucidate its underlying mechanisms using a rat model of cyclophosphamide (CYP)-induced interstitial cystitis. In comparison, chronic pain progression, histopathological features, and cytokine levels demonstrated that PTE mitigated the severity of symptoms in CYP-induced rats by inhibiting the NLRP3 inflammasome in a dose-dependent manner. Further mechanistic investigations indicated that PTE intervention alleviated oxidative stress in CYP-induced IC in rats via activation of the Nrf2/HO-1 signaling pathway. Moreover, inhibitors of the Nrf2/HO-1 pathway effectively blocked PTE-mediated attenuation of oxidative stress. The suppression of NLRP3 inflammasome activation by PTE could also be reversed by inhibition of the Nrf2/HO-1 pathway. In vitro studies revealed that PTE enhanced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and suppressed NLRP3 inflammasome activation in SV-HUC-1 cells exposed to lipopolysaccharide (LPS) and Adenosine Triphosphate (ATP). These findings collectively suggest that PTE treatment inhibits oxidative stress and suppresses NLRP3 inflammasome activation through modulation of the Nrf2/HO-1 pathway.