Display omitted •1. Rice bran rancidity increased the content of phenolics in rice bran dietary fiber.•2. Rancidity enhanced dietary fiber antioxidant properties during intestinal digestion.•3. Digestion released endogenous phenolics from rice bran dietary fiber.•4. During digestion, phenolics content determined dietary fiber antioxidant ability. Rice bran (RB) as the raw material for rice bran dietary fiber (RBDF) extraction, is rapidly rancidified prior to stabilization. To enhance the RBDF utilization in food industry, effects of RB rancidity (RB was stored for 0, 1, 5, 7, and 10 d) on the bioaccessibility and bioavailability of RBDF-bound phenolics were investigated. With the increase in RB storage time, the RB rancidity degree significantly increased (the acid value of rice bran oil from 5.08 mg KOH/g to 60.59 mg KOH/g), and the endogenous phenolics content in RBDF also increased. Simultaneously, RB rancidity reduced the antioxidant activity of RBDF digestion products during the gastric digestion phase, while RB rancidity increased the antioxidant activity of RBDF digestion products during the intestinal digestion phase. In addition, in vitro gastrointestinal digestion stimulated the release of RBDF-bound phenolics. The released monomeric phenolics (especially ferulic acid and p-coumaric acid) were the major contributors to the increased antioxidant properties of RBDF digestion products. RBDF digestion products could inhibit H2O2-induced oxidative stress and apoptosis of HUVECs. In conclusion, the study found that RB rancidity could improve the antioxidant capacity of RBDF in the small intestine by promoting RB endogenous phenolics bound to RBDF release.