This study explores the mathematical problem-solving process of trainee teachers in a teachers' training institute. This research adopts a constructivist perspective that views learning mathematics as a process of constructing meaningful representation and knowledge as being constructed by the individual. The research methodology employs the case study using interpretative approach. Three trainees majoring in mathematics from the Post Graduate in Teaching Course were selected by purposive sampling. Data were collected by audio and video taping the trainee teachers while they were solving three tasks individually using the "think-aloud" technique, followed by retrospection and clinical interviews. The findings revealed that the problem-solving process of the trainee teachers did not progress in a linear manner but rather moved back and forth with the earlier phases of problem solving in a cyclical nature. (Contains 3 tables and 2 figures.)