Children staying in social welfare institutions are exposed to numerous psychosocial risks. Separation from the biological family and placement into a social welfare institution in itself represents a stressful and/or traumatic situation for the child, and extended exposure to various risks during placement additionally leads to the development of complex post-traumatic symptoms. It is important to consider how professional workers of social welfare institutions can contribute to the preservation and improvement of children’s mental health, and this paper describes the possibility of combining the approach of transactional analysis and non-directive play therapy skills in treatment work. Transactional analysis, as a school of psychotherapy, is based on humanistic principles and has a long tradition of psychotherapy work with children and adolescents in individual work with children. As a personality theory and developmental theory, it offers a framework for understanding the development of dysfunctional and rigid patterns of behaviour and experience, the so-called script. In getting rid of such patterns and preventing their development, combining the approach of transactional analysis with the application of non-directive play therapy skills has proven to be successful in working with children. Play therapy allows children to practice different skills, explore the world, objects and relationships between people, and resolve internal conflicts in a safe and supportive environment. This is achieved through three key skills of non-directive play therapy: empathic reflection, therapeutic boundary setting and encouragement, which we describe through examples from work with children placed in social welfare institutions.