In order to examined the response of berries physical and chemical properties of Superior Seedless grapevines to spraying seaweed extract (at 0.1%, 0.2% & 0.4%) and chitosan (at 0.05%, 0.1% & 0.2%). A field experiment was conducted during 2018 and 2019 seasons in clay soil, under Matay district conditions, El-Minia Governorate, Egypt.  The obtained results showed that spraying both examined materials (seaweed extract and chitosan) in combination was more effective than using each one alone on berry physicochemical parameters. The vines received seaweed at 0.4% and chitosan at 0.2% in combination produced the best berry physicochemical properties. However, non-significant differences between the two highest concentrations of both examined compounds (seaweed and chitosan) were observed. From these standpoints it is strongly recommended to spray ‘Superior Seedless’ grapevines grown in clay soil with seaweed extract at 0.2% + chitosan at 0.1% three times yearly in order to improve all physicochemical properties of berries.