This book provides a brief theoretical overview of transactional analysis theory and brings together results from research conducted over the past few years studied the influence of the functional ego states and the life positions on the subjective career success. The aim is to reveal the relationships between the personality constructs proposed in transactional analysis theory with the subjective career success and the vocational choice. The main concepts for describing personality in transactional analysis theory that are having a significant impact on a person‘s functioning in adulthood and interaction with other people as structural and functional model of ego states, transactions and strokes, life positions, script and drivers are presented as personality characteristics formed predominantly in early childhood. The concept of games and their function related to time structuring and ensuring the stability of personality behavior is briefly discussed.