Abstract: The aim of the study was to determine the effect of the addition of 0, 1, 3, and 6% of Spirulina powder (SP) on physicochemical properties and consumer acceptability of shortbread biscuits during storage. Color, hardness, water content, water activity, total antioxidant activity (TAA), total phenolic content, lipid oxidation, fatty acids profile, and sensory evaluation of biscuits were determined on 0, 30, 60, and 90 days of storage. Results showed that biscuits baked with the addition of SP were significantly harder and darker than the control during the whole period of storage. Despite this, they were still acceptable by consumers. It was observed that in each day of storage biscuits with SP had more phenolic compounds and higher values of TAA than the control, and their contents increased with the level of SP addition. Moreover, the addition of SP reduced oxidative changes of shortbread biscuits during storage. Practical Applications: Intense competition in the market of biscuit manufacturers forces to implement product innovations in order to attract new groups of consumers. Shortbread biscuits with Spirulina powder could be characterized not only by nutritional properties and quite good sensorial acceptability but also by extended shelf life. Additionally, so far products identical with the proposed have not been observed, which creates great opportunities for their commercialization. [ABSTRACT FROM AUTHOR]