At the INRAE organic experimental station, piglets are weaned at 49 days of age. At this age, individuals are heavy, and fights between litters can sometimes be violent. As early socialisation was reported to decrease aggressiveness at weaning, we performed a trial with four batches of pigs from March to September 2023. From 21 days of age, in each batch, piglets from six litters in the “socialised” group were given the opportunity to mix in the maternity pens, with their mothers remaining in their 10 m² pens. Each of the other six litters was kept separate. At weaning, the socialised piglets were separated by sex, while the piglets reared per litter were pooled and then separated by sex. The four groups thus created, which contained approximately 30 pigs each, were then kept unchanged until slaughter. Growth under sows and post-weaning performance were measured. Post-weaning scratches were counted, and hair cortisol was measured as an indicator of chronic stress level. The overlapping behaviour of males at the end of fattening was also assessed. Early socialisation significantly decreased pre-weaning growth only in males, with no other effect on growth until slaughter. At weaning, hair cortisol was significantly lower in socialised females than in control females. Finally, as expected, early socialisation significantly decreased the aggressiveness of piglets at weaning. Altogether our data confirm that early socialisation of piglets is a tool to increase animal welfare in commercial farms.