Using an experimental approach, our study examined the differentiated effects on pre-schoolers' social cognition of two short-term social information processing (SIP) and Theory of Mind (ToM) training sessions dealing with emotions and beliefs. The links between ToM, SIP, and social adjustment or externalizing behavior were examined. 47 pre-schoolers took part in a pretest session involving cognitive, socio-cognitive and social adjustment measures. The direct socio-cognitive measures involved tasks assessing emotion recognition, ToM emotions, ToM beliefs and social problem-solving. The teachers filled out a personality questionnaire and parents completed the Theory of Mind Inventory, a social adjustment scale and the CBCL. Secondly, they were allocated at random to two experimental groups (ToM training or SIP training) or to a control group. In the experimental groups, each of three children, short training sessions were given using educational materials. Free play was offered in the control group. Finally, all children took part in a post-test session. Our results showed significant improvement in ToM emotions for the ToM training group, in ToM beliefs for the SIP training group, and in social problem-solving for both experimental groups, and some transfer learning. In pretest, significant positive correlations were obtained between social cognition measures and individual characteristics, and between social cognition measures and social adjustment. Significant negative correlations were observed between social adjustment and externalizing behavior, and between social adjustment and emotional reactivity. This study provided some guidelines for formulating a medium-term training program in social cognition aimed at pre-schoolers at risk of displaying externalizing behavior disorders.