The ability to understand mathematical concepts is still low. Efforts are needed to overcome these problems, including using the Think Pair Share and Problem Based Learning learning models. The research was conducted to determine the improvement and quality of the improvement in students' mathematical understanding abilities with the two learning models. The research method is quasi-experimental with a population of all seventh-grade students of one of the public junior high schools in Garut. Samples were chosen randomly, namely class VII-G as experimental class I and class VII-H as experimental class II. The instrument is a description test. The results showed that the improvement and quality of the improvement in the ability to understand mathematical concepts of students who received the Think Pair Share learning model was better than Problem Based Learning. Think Pair Share learning model is more recommended to be applied in improving the ability to understand mathematical concepts.