The present experiment aimed at evaluating the relative effects of environmental and social changes on behaviour, growth and salivary cortisol of piglets at weaning. On Day 0, 26-day old piglets were weaned and allocated to one of four treatments: neither environmental nor social change (C), environmental change (E), social change (S), and both changes (SE). Overall, 6 replicates of 10–12 animals/pen/treatment were analysed. Piglets were video recorded during the first three days after weaning to observe social behaviour and general activity. Saliva was collected between 07:00 and 09:00 on Day 0 just before weaning (D0H7), on Day 1 (D1H7) and Day 2 (D2H7 and D2H16) to measure cortisol. Saliva cortisol did not change after weaning in C piglets but increased significantly at D1H7 in S and SE piglets, at D2H7 and D2H16 in E and SE piglets. Compared to C piglets, numerous behaviours were altered in SE piglets: more total lying (P < 0.08), less lying on the belly, less environmental exploration, less playing, more fighting regardless the day, more lying awake inactive on Day 0 (P < 0.05). Compared to C piglets, E piglets displayed more total lying but less environmental exploration whereas S piglets showed less lying on the belly but more fighting (P < 0.05). Present results show that moving piglets to a new environment as well as mixing them with unfamiliar conspecifics at weaning have stressful effects which are additive.