The effect on the bitterness and taste of tea was studied of fermenting non-sterilized leaves with Aspergillus. A treatment with A. oryzae reduced the levels of both epigallocatechin gallate (EGCg) and epicatechin gallate (ECg), which tend to give a strongly bitter taste, and increased the levels of epigallocatechin (EGC) and epicatechin (EC) that can be easily ingested. The treatment also increased the levels of amino acids like Glu and Asp that are responsible for the umami taste. The results suggest that fermenting leaves with A. oryzae may provide a better taste and improve the ease of absorption of tea.