Pattern recognition is an aspect of computational thinking and a vital competency for solving mathematical problems. By recognizing patterns, one can develop possible solutions. This paper aims to describe the pattern recognition of prospective mathematics teachers in solving mathematical problems from a semiotic perspective. This study based on a qualitative case study approach. The research subjects were prospective mathematics teachers from a private university in Indonesia with impulsive and reflective cognitive styles. The data was collected using mathematical problem-solving tasks and interviews. Research findings indicate that individuals with impulsive and reflective cognitive styles employ a five-sign trichotomous process for pattern recognition. In the trichotomous system of signs, the final object is the pattern, like a determine the triangle height. The representamen consists of mathematical equations, such as equations with variables height. The interpretant is to determine patterns from the solved mathematical equations. In the case of the given problem-solving task, both students determine the height of a triangle. Further research is recommended for problem-solving activities conducted in groups so that the object, representamen, and interpretant from various student perspectives can be understood.