Teacher training continued as having rigid boundaries and stages in the 19th century. At the same time, teaching was regarded as a low-status profession. Teachers were trained within their profession and schools in this period. This type of training was carried out with trainee teachers working in primary schools. The aim was to train teachers as modest, earnest, observant of customs, obedient to moral norms and unquestioning individuals. However, it was realized that teachers having intended qualifications could not be trained by means of these methods. New emerging demands in 1980s caused a consensus on a set of tenets about what type of issues should be placed in teacher training programs. In this framework, new understanding aroused that teachers should be equipped with the knowledge of child development, learning theories and teaching methods, sociology and psychology and has competencies in subject matter knowledge and teaching methods. Besides these, the dimension of social justice and reconstruction of society was added to the conventional role of teachers in 1980s. It was understood that if it was aimed to obtain success in educational reforms and development of schools, at the same time, it was necessary to improve pre-service and in-service teacher training in 1990s. Teacher training was based on the cooperation model between higher education and schools in 2000s. In this period, the fundamental concept which came into prominence was concerned with teachers who had these features: possess comprehensive knowledge and competent in implementation, questioning, visionary, has the ability to digress from ordinary rules in the classroom and providing students with the freedom of saying their opinions. (Dillon and Maguire,1998: 30-36). In the 21st century, however, the understanding which stresses the fact that teachers should be involved in tasks such as educational reforms, renovation, and development and be part of these processes became prominent. In today’s perception is shifted towards the view that rather than taking and implementing the content, curriculum and methods as they are, teachers are expected to form every situation related to their own materials, methods, in-class activities and instruction (Nunan, 2004: 133). Towards the end of the 20st century, all developed, developing and underdeveloped countries were in search of finding different and effective ways to prepare their citizens for the life in the 21st century by training their citizens and obtain success in education at both international and local levels. In this context, four dimensions about redesigning and modernizing educational content come to forefront: 1- Learning for knowledge. 2- Learning for doing/performing. 3- Learning for existing. 4- Learning to live together. The most critical dimension is “learning to live together”. Learning to live together is the prerequisite for achieving the other three factors. The tenets which define these dimensions are 1- Constructing awareness for citizenship. 2- Make disadvantaged groups advantageous. For this reason, teachers’ participation into every kind of educational reform applications maintained and it is necessary to train teachers as competent in the 21st century understanding and tendencies. From this aspect, it obvious that there is a need for all countries to renewing, modernizing and altering their teacher training program in accordance with the demands of the 21st century. Factors such as disappearance of personal, social and geographical boundaries, contemporary understandings and the necessity of implementing these resulted in multidimensional and multicultural perception of citizenship. This new understanding as well as tendencies renders renewing teacher training and in-service training programs compulsory. Characteristic of the 21st century society is to have a philosophy of life which is differentiating in terms of culture and perception and gradually globalizing. Values and issues such as increasing diversity in culture and language, international dialogue, having access to information instantly, socio-economic inequality and inability of wide range of people to benefit from democratic rights are becoming eminent in the 21st century. In this context, since teachers are the first group that changes influence, it is essential to prepare teachers for the 2st century and its requirements. Qualified teacher training is fundamental in maintaining teacher participation effectively and voluntarily in reform movements to be held in education. Teacher is the most essential and significant component of every kind of renovation to be made in education. Teachers should have active participation in every type of educational reforms. In this framework, the study is based on two problems. One is to put forward the qualifications of the 21st century teacher in accordance with features of the 21st century society and new foremost understandings and issues. The second, in this context of new understandings and issues, it is tried to determine dimensions of teacher training programs in the 21st century. Research is a theoretical study. Compilation method was utilized in this study. Data were obtained by means of studies about the research problem in related literature and conducted within the last ten years. Then, collected data were analyzed based on research problems. On the basis of these analyses, tendency and issues, new concepts required to form the basis of pre- and in-service training of teachers and tenets and understandings about teachers in the 21st century were inferred. The study gave way to the following results: 1- Teacher training programs should be conducted on an international basis. 2- The 21st century teacher should be trained as having multicultural understanding and competency. 3- Teachers should be trained with the perception of building a cross-cultural education and democratic society. 4- Vital compone