We studied how addition of granulated higher fatty acids (GHFA) would affect nitrate and ammonium leaching out of pots planted with tea plants. In Wagner pots (1/5000a, height 30cm) filled with tea field soil, we mixed GHFA into the upper soil layer (depth 10cm) at 0 (control, without GHFA), 0.5, 1, or 5% (0, 10, 20, 100g per pot), and cultivated tea plants (Camellia sinensis (L.) var. sinensis) for approximately one month. We measured the leaching of nitrate and ammonium from the pots over this period by monitoring ^<15>N-labeled potassium nitrate or ammonium sulfate that had been applied to the pots. We found the following: 1) GHFA applied at 5% reduced leaching of nitrate in drainage water by 40% and ammonium concentrations in drainage water by 20%, compared to control pots. 2) At the end of treatments, the content of inorganic nitrogen in the upper soil layer with GHFA was higher than that of the soil without GHFA. In addition, the content of ^<15>N retained in soil was also higher in GHFA treatment. These results suggest that the decline of leached nitrogen from pots with GHFA was caused mainly by immobilization of nitrogen rather than denitrification. 3) The growth of tea plants cultured in the pots with GHFA applied at 5% was not suppressed, but was vigorous compared to that of control pots. The content of total nitrogen of tea plants also increased in the 5% GHFA treatment. Therefore, we suggest that the application of GHFA up to 5% is useful to increase nitrogen uptake, stimulate tea plant growth, and reduce nitrogen leaching by retaining it in the soil.