The paper analyzes the topics of lifelong learning, career development and the impact of lifelong learning on teacher career development. Theoretical determinants of career management and development are defined. Career has become an important concept that has great significance for all working people. A career is a prerequisite for achieving a quality standard of living and reputation in society in the world of the 21st century. The meaning of the term career is interpreted and career management is defined. The most significant theories of career development from the literature are explained, career types are classified and different stages in career development are explained. Attention is paid to motivation as a key factor influencing career development. It describes how to make an effective career development plan and career development strategy. The concept of lifelong learning and its meaning are carefully defined. The positive effects of lifelong learning on adult education are explained. The extremely positive impact that lifelong learning has on employment and career development are analyzed. Lifelong learning greatly helps people to be more competitive in the labor market, find employment easier and have significantly greater opportunities to advance their careers. Special attention is paid to the lifelong education of teachers, which is the central theme of the thesis. It is described that the system of lifelong learning is an important tool through which teachers acquire intercultural competencies that are becoming increasingly important in recent times. A research was conducted in the form of a survey questionnaire that investigates how lifelong education affects the development of teachers' careers in primary schools in the Primorje-Gorski Kotar County. The results of the research showed that thanks to lifelong learning, teachers strengthen all competencies and develop their careers more easily. Based on the collected data and their analysis, a proposal of guidelines for the improvement of lifelong teacher education in the Republic of Croatia is presented.