Animal contests are costly and predicted to be won by the individual with the higher resource-holding potential (RHP). Weight is often used a proxy for RHP; however, victory does not always go to the heaviest competitor, indicating that other traits may also contribute to RHP. Here we investigated the effect of preweaning play-fighting experience on postweaning contest behaviour in the domestic pig, Sus scrofa. We predicted that individuals that played more would win contests later in life. Play-fighting experience was also predicted to influence contest escalation behaviour, on both an individual and a dyadic level. Lastly, a pre-established framework and eight contest cost measures were used to establish whether competing individuals gather/use information regarding play-fighting experience as part of an assessment strategy. Play-fighting experience was recorded for socialized and control litters before weaning and contests were staged between unfamiliar pigs of the same treatment after weaning. Controlling for competitor weight difference revealed that increased play-fighting experience was linked to contest success in females, while the opposite pattern was found in males. Play-fighting experience did not influence which individual within the dyad escalated contest behaviour, but dyads containing more experienced losers were more likely to perform a stage of nondamaging aggression. When we used skin lesions in losers as a measure of contest cost, we found evidence for the role of play-fighting experience in a novel mutual assessment strategy in socialized dyads, whereas control dyads performed opponent-only assessment. We suggest that while assessments of RHP can be made using a physical correlate of play-fighting experience (such as skillfulness), early life socialization is required for individuals to gain an understanding of their own RHP. (C) 2019 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.