Abstract. This study explored the features of prospective teachers' thinking process skills in the process of solving an ill-structured problem in an private university mathematics classroom in Makassar, Indonesia. The participants solved the ill-structured problem by following the phases of Analyze, Browse, Create, Decision-making, and Evaluate. Thirty prospective teachers were selected to complete the mathematical ability test. The students were classified into high and low-ability groups. The group of high-ability prospective teachers were interviewed based on the results of solving the Ill-Structured Problem. Firstly, analyze: understanding and redefining the problem by connecting and presenting known information on the problem through image representation. Secondly, browse: identifying the mathematical content needed to solve the problem. Thirdly, create: formulating solutions that meet many conditions and showing alternative solutions to problems in written and oral form. Fourtly, decision-making: finding the relationship between the solutions contained in a given problem. Lastly, evaluate: identifying a problem-solving idea as a follow-up plan when faced with a relatively similar problem and completing a written solution. This finding study suggested that it can be employed to help detect the features of prospective teachers' thinking process to solve ill-structured problems in mathematics education.