Children's problem behaviour in the preschool period is a severe obstacle to social-emotional development and a precondition for maladjustment in social relationships during school life. Professionals in the field have been improving existing practices to prevent and intervene in young children's challenging behaviour. To this end, many social-emotional learning curriculums are developed and put into practice. One curriculum that supports children's social-emotional learning during the preschool period is the Second Step Early Learning. The present study looked into the practical experiences of preschool teachers implementing the second step social-emotional learning curriculum. The study group consists of 13 preschool teachers who have received educator training in this learning curriculum and implemented it at schools. The teachers were asked questions about the curriculum's general qualities, its effects on the children's development levels, and their professional development. According to the study results, all teachers stated that the second step curriculum positively contributed to children's emotional and behavioural reactions. It helped them in class management and implementation, such behaviour as having confidence, asking for help, taking responsibility, and taking responsibility-sharing improved. In addition, expressing that they observed differences in hindering anger and in-class problem-solving processes, teachers emphasised that the children were more understanding and polite to each other, especially in free-time activities. Their interaction was healthier than before, and their listening and attention spans increased. Overall, the findings show preschool teachers' experience in implementation. They recommended the curriculum to their colleagues, claiming that it contributed to their professional development.