In recent years, studies have shown that seaweed applications could prevent post-harvest berry drops in grapes and allow improvements in cluster and berry quality characteristics. This study was conducted on 'Tarsus Beyazi' grape cultivar, which was grown on its own root and goblet-trained, in the Tarsus district of Mersin Province, Turkey. Although 'Tarsus Beyazi' is an early and well-known cultivar, it does not attract much attention due to its genetic susceptibility to berry drop; however, it is an important grape genetic source. In this study, foliar spraying of seaweed (Ascophyllum nodosum [L.] Le Jolis) was applied to the vines of 'Tarsus Beyazi'. After the application, the force to separate the berries from the stalk, berry weight (g), berry width (mm), berry length (mm), cluster width (cm), cluster length (cm), cluster weight (g), titratable acidity (%,TA), total soluble solids (%,TSS), and pH, as well as leaf and berry mineral content, were determined. Based on our results, it was determined that seaweed application had positive effects on the cluster characteristics rather than the berry properties of the 'Tarsus Beyazi'. The difference between application and control grapevines was found to be significant for cluster width and weight. As compared to the control grapevines (11.16 cm), clusters were approximately 9.86% wider in the application grapevines (12.26 cm), and the difference in cluster weight was about 37 g between the mean value of the application (297.40 g) and the control (260.23 g) grapevines. To sum up, the use of seaweeds in 'Tarsus Beyazi' has made it possible to improve grapevine productivity and enhance berry quality, mostly in terms of cluster characteristics.