Play in the Columbian ground squirrel (Spermophilus columbianus) was examined using marked individuals in a population in southwestern Alberta, Canada. The components of play varied with the age, sex and relatedness of the interactors. Only in intra-sexual play were differences apparent in littermate and non-littermate play. Male-male non-littermate play had fewer contact behaviours than littermate play, whereas female-female non-littermate play had escalations in aggressive-related behaviours. Yearling play was longer and had more aggressive-related behaviours than juvenile play. Reversals were more common in yearling bouts. The significance of those differences in social play that were related to sex, age and relatedness are discussed in light of the social organization of the Columbian ground squirrel.