The aim of the study was to determine the arithmetic and algebraic problem-solving approaches of prospective mathematics teachers in the Department of Elementary Mathematics Education, and mathematics teachers in secondary schools. The study adopted mixed methods research design using exploratory sequential pattern. The participants of the study were composed of 128 prospective teachers (59 sophomores, 41 juniors and 28 seniors) in the Department of Elementary Mathematics Education in a state university and 22 secondary school mathematics teachers in different cities of Eastern Anatolia Region of Turkey. Clinical interviews were conducted with 12 prospective teachers and 5 teachers. The data were obtained via the Problem-solving Test [PST] and a semi-structured interview form [SSIF]. The PST was prepared to examine the problem-solving processes of the teachers and prospective teachers participating in the research. He findings of the study revealed that both groups of the participants preferred the algebraic approach while solving problems, and could not make use of the arithmetic approach. It was also understood that they had tendency to use algorithms they knew by heart while conducting algebraic solutions. As a consequence, these results showed that the participants had some deficiencies in terms of bringing both arithmetic and algebraic solutions to mathematical problems.