Constructivism has been increasingly spreading in the educational systems of the developing countries. Because, there is strong evidence suggesting that constructivist applications are one of the ways to make students acquire searching, problem-solving, and creative and critical thinking skills. Students gain these skills most in science and technology courses. A significant role has been expected from science teaching in primary education level in turning students into conscious citizens of 21(st) century and forming a solid base for the society. The main function of science teaching in primary education is to prepare individuals for the future and life. All developed countries have revised their science education provided at primary schools and reflected the innovations into their programs. Turkey also has reflected these innovations in its programs and prepared a science teaching program based on the constructivist theory. The main purpose of this study is to discuss the constructivist theory, which is considered to be one of the contemporary approaches the most apt for the application of student-centered teaching in science teaching and to put across the problems that are encountered while reflecting this theory into practice in Turkey.