'Ruby Seedless' is a good alternative for quality seedless table grape (Vitis vinifera L.) production for the Comarca Lagunera. Objections for increasing the area planted to 'Ruby Seedless' in the region are berry size and less tolerance to handling than that of current seeded cultivars. The objective of this study was to determine the effectiveness of trunk girdling and gibberellic acid (GA) application on berry weight increase in low and high vigor four year old Ruby Seedless grapevines. Four treatments were applied on low and high vigor grapevines: a) Trunk girdling (4.7 mm); b) Two GA cluster applications of 40 mg L⁻¹ one week apart: c) Girdling and two GA applications of 40 mg L⁻¹; and d) Untreated control. Vines were girdled at fruit set, and the first application of GA was done one week after girdling. Berry weight for low vigor vines was 30.4% lower than that in vigorous plants. Girdling ang GA applications had no effect on berry weight in low vigor vines, but the untreated control had the tendency to bigger berries. Two sprayings of 40 mg L⁻¹ of GA did not significant increase berry weigh from the control treatment in high vigor vines. Girdling caused a significant (p ≤ 0.05) increase in berry weight (14 %), compared to the untreated vines, and a significant (p ≤ 0.05) delay in fruit maturity, which resulted in 1.7 °B less than that observed in the untreated vines. Trunk girdling was more efficient than application of GA in increasing berry weight in Ruby Seedless grapes, but it delayed maturity. In vines with low vigor, these practices tended to reduce berry weight.