Social interactions, including collaborative problem-solving situations, can trigger critical thinking skills. Giving questions that are not routine can trigger students' critical thinking skills in solving problems collaboratively. This research aims to develop non-routine mathematics problems that can be used to explore students' critical thinking abilities in collaborative problem-solving. The research results show that questions with problem criteria that require justification for the solution provided and questions with a graphical analysis approach can be used to explore students' critical thinking skills in collaborative problem-solving. This is proven by solving the problems; each group member contributed to the solution-finding process. The contribution of each group member shows the high intensity of interaction between members. Interaction in the form of exchanging opinions, giving suggestions, and evaluating each other's ideas or answers significantly impacts students' critical thinking abilities. This is seen by the emergence of several students' critical thinking skills (analysis, synthesis, argumentation, evaluation, self-regulation) triggered by suggestions or ideas put forward by other group members. The research results can be a reference for researchers or practitioners exploring critical thinking skills as a guide in developing research instruments.