Oxidative stress-induced mitochondrial disturbance plays a critical role in the progression of acute kidney injury and its transition to chronic kidney disease. Food-derived bioactive components have received long-lasting attention in nutraceutical therapy for various kidney diseases. Flazin is a food-derived β-carboline alkaloid widely discovered in fermented foods and fruit juice. In the present study, flazin was studied for its mitochondrial-improving effects on renal tubular epithelial HK-2 cells under oxidative stress. Flazin protected HK-2 cells from oxidative stress-induced cell death by reducing reactive oxygen species levels, decreasing mitochondrial-dependent apoptotic genes expression, and increasing antioxidative genes expression. Moreover, flazin improved mitochondrial dynamics by restoring mitochondrial branched structure and increasing length as well as network size through regulating fission/fusion-related genes expression. Flazin also improved the profile of mitochondria-specific phospholipid, cardiolipin, including increasing its content, improving its species, and reducing its hydroperoxides ratio through regulating cardiolipin biogenesis and remodeling genes expression. These resulted in increased ATP production and enhanced mitochondrial function. This study highlights the health-beneficial effect of flazin on cellular redox homeostasis and mitochondrial dynamics, suggesting it may serve as a daily nutraceutical to contribute to the prevention and treatment of kidney disease related to oxidative stress and mitochondrial disturbance. © 2023 Elsevier Ltd