Starting in 2022, Thompson seedless grapevines (H4 strain) received 50 kg of actual nitrogen per Fed. (about 71.4 g N/ vine) combined from three different sources for two consecutive seasons. Control plants received 100% fast-release nitrogen fertilizer (NH₄NO₃ 33.5% N). Treatment groups received triple combinations of 50% or 25% from NH₄NO₃, 25% or 37.5% organic N fertilizer (plant compost, 2% N), and 25% or 37.5% from one slow-release N fertilizer, namely urea formaldehyde (UF, 38.37% N), phosphorus-coated urea (PCU, 37.11% N), or Sulphur-coated urea (SCU, 41% N). The target was to select the best ratio and the preferred source of slow-release nitrogen. Using nitrogen as 25% NH₄NO₃, 37.5% plant compost, and 37.5% slow-release nitrogen (UF, PCU, or SCU) significantly improved berries' growth, yield, and physicochemical properties compared with other treatments. The results showed that the best slow-release nitrogen sources were SCU, PCU, and UF. Conversely, an apparent reduction in these traits was in the vines treated with 100% nitrogen as ammonium nitrate. To enhance the growth, yield, and cluster quality of Thompson Seedless grapevines (H4 strain), it is recommended to utilize a combination of nitrogen fertilizers: 25.0% fast-release (NH₄NO₃), 37.5% organic (plant compost) and 37.5% slow-release (e.g., SCU).