The paper presents results of a longitudinal study on child temperament in infancy and early childhood and the possible impacts of socioeconomic status of a child’s family on his/her mental health in the future. The study involved 100 children and employed a set of questionnaires for parents: the Infant Behavior Questionnaire (IBQR), the Early Childhood Behavior Questionnaire (ECBQ), and the Strengths and Difficulties Questionnaire (SDQ) for assessing mental health, and a separate social questionnaire. The outcomes indicate that volitional regulation is an important factor in preventing mental health issues in the children; its predictive impact varies between 4 and 20%. Among the average level dimensions the highest impact was that of Low-intensity Pleasure. Socioeconomic status of the family, on the opposite, was found not to have any significance in predicting the future mental health of the child. All in all, this longitudinal research contributes greatly to the understanding of how infant and early childhood temperament and socioeconomic characteristics of the family shape the prospective mental health in Russian children.