Purpose Silicon (Si) acts to reduce biotic and abiotic stresses in plants. Herein, we aimed to assess the impact of an amorphous silica-based fertilizer (ASF) applied to soil on the yield, mineral nutrition, chlorophyll fluorescence, and postharvest quality of two cultivars of table grapes grown in a semiarid climate. Methods The cultivars Arra 15 and BRS Vitoria were submitted to the treatments control, 175 or 350 kg ha(- 1) ASF. Leaf and fruit samples were collected and analyzed for Si, nutrients, and postharvest quality characteristics. Photosynthetic efficiency was assessed by measuring chlorophyll a fluorescence. Results Both cultivars showed significant responses to Si with the ASF rates of 175 and 350 kg ha(- 1). The characteristics improved through ASF application compared to the control were: fruit production (6-22%), bunch weight (11%), number of berries (20-34%), berry crunchiness (20%), the content of total soluble solids (13-20%), the titratable acidity (13%), the accumulation of macro and micronutrients (12-45%) and the photosynthetic efficiency (5-33%). Conclusion Soil-applied Si increases the yield and quality of grapes by improving the plant response to abiotic stresses, being such effects more significant in the dry season.