Foliar and fruit application of mineral particle films is considered to reduce damage from heat and water stress significantly in many horticultural crops. Sprays with new formulations consisting of suspensions of calcium carbonate can have beneficial effects on vegetable crops, including tomato. We assessed the effects of a calcium carbonate suspension on physiology, yield and some quality aspects of a tomato crop under three levels of deficit irrigation (I₅₀, moderate; I₂₅, moderate–severe; I₀, severe) in the semi-arid climate of eastern Sicily. Leaf transpiration was significantly reduced by 47% (late June) and 58% (early July) in plants treated with the suspension. Late in the growing season, sprayed leaves were ∼1°C cooler than unsprayed (control) leaves. Spray treatment resulted in a higher marketable yield (+12%) than the control under I₅₀, and fruit quality was significantly improved under I₀. Treated tomatoes exhibited better firmness (+24%), higher contents of vitamin C (+15%) and total phenols (+12%), and higher antioxidant activity (5–7%) than untreated tomatoes. Application of calcium carbonate minimised fruit losses under I₅₀ while ensuring great water saving and improving the nutraceutical properties of fruits. These aspects make the technology an environmentally friendly tool to improve crop sustainability and nutritional quality in tomato.