Grafting of tomatoes has the potential to increase tomato seed production under organic conditions. Grafting means to combine the positive characteristics of a rootstock (e.g., increased vigour, resistances to soil-borne diseases) with the positive characteristics (e.g., fruit quality, taste) of the upper part of the plant (scion). We compared the seed production of three tomato cultivars: ‘Benisoda’, ‘Berner Rose’ and ‘Rosa de Barbastro’, which were either non-grafted (NG), or grafted on ’Emperador’ (Rijk Zwaan) or on a BRESOV rootstock (interspecific hybrid S. glycopersicum x S. habrochaites provided by UPV, Spain). Plants were grown under organic conditions in the greenhouse at Terre d’Essais, Britany, France. Fruit number and weight were measured throughout the season of 2021. Seed weight, number and Thousand Seed Weight (TSW) were assessed on the first two bunches. Overall seed production was extrapolated based on total fruit production