BACKGROUND: Whey, a nutrient-rich byproduct of the dairy sector, possesses high potential for creating novel nutraceutical products. The present study investigates a potential new functional food by incorporating polyphenolic extracts from Myrtus communis and Arbutus unedo fruits into whey in both liquid (LA) and powder (PA) addition forms. Chemical, microbiological, physical stability and antioxidant activity were monitored for 60 days (from T RESULTS: Both LA and PA of fruit extracts remained chemically stable for the whole period, except for A. unedo PA, which showed a decline in polyphenols after T CONCLUSION: Whey enriched with Mediterranean fruit extracts shows great potential as a functional food, combining the benefits of plant antioxidants, probiotic bacteria and good stability. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.