This study was aimed to 1) produce a contextual-based module to improve students' mathematical critical thinking skills which has a validity aspect. 2) produce a contextual-based module to improve students' mathematical critical thinking skills which have a practical aspect. 3) produce a contextual-based module to improve students' mathematical critical thinking skills which have an effective aspect. Pre-test and post-test were done to obtain themeffectiveness and practical aspects. In producing this module, the researcher used ADDIE development which has Analysis, Design, Develop, Implementation, and Evaluation stages. The researcher conducted product trialsat SMP Negeri 3 Kroya in 7th grade with a sample of 8 students. From the results of product trials on the effectiveness and practical aspects, it was found that the developed module was valid and suitable to be used as learning materials. The score results from the validator have been said to be valid and feasible. From the results obtained, it can be concluded that the contextual-based module to improve students' mathematical critical thinking skills is said to be feasible and can be interpreted as valid, practical, and effective.