The resource, or strength, model of self-control (Baumeister, Heatherton & Tice, 1994) suggests that individuals possess a limited resource of strength, or energy, which is depleted by acts of self-control, leading to reduced performance on a subsequent, unrelated, self-control task (Muraven, Tice & Baumeister, 1998). This decrease in self-control has been labelled ‘ego depletion’ (Baumeister et al., 1998). Review of the research literature reveals an impressive array of effects linked with ego depletion; however, the majority of these studies have focused on depletion in adults. The present study aimed to extend the research literature in this area by investigating the ego depletion effect in 89 primary school children aged between 10 and 11 years. A dual-task procedure was used to investigate the potential ego depletion effect of a brief thought suppression task upon a subsequent task of receptive attention. In addition, the current study aimed to find out whether trait mindfulness (i.e., a disposition towards open and non-judgemental awareness of one’s self and attention to the moment) can counteract ego depletion in children (Baer, Smith, Hopkins, Krietemeyer & Toney, 2006; Bishop et al., 2004; Brown & Ryan, 2007a). No significant effect of ego depletion on performance in the second self-control task was found. A borderline significant effect of ego depletion on the children’s perceived difficulty of the second self-control task was found. Trait mindfulness was found to be a significant predictor of children’s perceived difficulty of the second self-control task. No significant moderation effect of ego depletion by trait mindfulness was found. Implications are explored and future directions discussed.