The present study was carried out during 2021 and 2022 growing seasons to examine the effect of individual or combined applications of some organic acids and seaweed extract. The treatments included on Thompson seedless grapevines (H4 strain) yield and its quality. Citric and ascorbic acids each at 250 to 1000 ppm, salicylic acid at 50 to 200 ppm and seaweed extract at 0.05 to 0.2%. The individual or combined applications of the antioxidants was very effective on improving the vegetative growth characteristics, vine nutritional status, yield and berry quality during both seasons of study. The best individual treatment was seaweed extract followed by salicylic acid and then ascorbic acid and finally citric acid. The combined application of these materials was more effective than individual use of each antioxidant on promoting growth characteristics. Also, the stimulation was proportional to concentration increases of each material. To promote yield and berry quality of Thompson seedless grapevines (H4 strain) grown on sandy soil, it is recommended to spray the grapevines three times at growth start, just after berry setting and one month later with a mixture consists of citric acid at 1000 ppm, ascorbic acid at 1000 ppm, salicylic acid at 200 ppm and seaweed extracts at 0.2%.