Beneficial properties of polyphenols are widely recognized, and polyphenols-rich olive oil has been identified as one of essential food for healthy effect of Mediterranean diet. However, over the past decade, the olive leaves have been discovered as an alternative rich source of polyphenols as well. Recent studies on olive leaves confirmed a high phenolic content that explain their previously described strong antibacterial, antimicrobial and antiviral activity. Therefore, the major aim of our work was to comprehensively determine olive leaves phenolic content in cultivars Istarska bjelica, Leccino and Buža, as natural source of bioactive compounds suitable for daily consumption in the form of tea. For this purpose, we examined the influence of olive leaf variety, maceration time and temperature on the final tea phenolic composition. Based on the obtained results, the method optimization was carried out. The level of success of the optimized method was determined with the organic extraction in methanol. Phenolic compounds were analysed by use of liquid chromatography coupled to triple quadrupole mass spectrometer (LC-QQQ). Finally, using the Design-Expert software, tea mixtures where designed based on the desired polyphenol composition. Expectedly, results revealed significant influence of the olive variety, but also maceration parameters on the quantitative and qualitative phenolic composition. The highest amount of phenolic compounds was obtained for Istarska bjelica after 15 min maceration. Samples of Buža an Leccino, although they contained less total amount of polyphenols, were distinguished by variety of the content. Furthermore, we designed several functional olive leaf teas mixtures with phenolic composition adjusted to the desired health effect. Results pinpoint the role of optimized phenolic composition in design and improvement of olive leaves teas quality.