The first part of this study is theoretical and deals with important theoretical assumptions and concepts of transactional analysis. The second part presents the results of research whose goal was to gain insight into the experiences of psychotherapists transactional analysis about the effectiveness of application counseling and psychotherapy by TA principles. Qualitative research was conducted and is based on experience of eight psychotherapists which applied transactional analysis in their counseling work. Content analysis and open coding is used in research to get the answers on the research questions. Based on the results it is concluded that the transactional analysis is psychotherapy direction with a strong theoretical assumptions and concepts that allows widespread use in counseling work. It helps in solving problems in everyday life and in the functioning of the various forms of personality disorders. Participants stress the importance of the concept of contracting in TA that makes easier and quicker achievement of the agreed therapeutic goals. The research results have shown that the key to success and further progress in work of continuing professional education and upgrading.