In this study, a mathematical modeling activity was designed and implemented in a seventh grade classroom. The students were first expected to examine a given mathematical model of a problem that is based on a real life situation and then build a model depending on their own criteria. The mathematical modeling activity which was designed by the researchers involves many mathematical concepts and processes such as analyzing data, reading a table, interpreting a table, building a model, drawing a graph, and interpreting a graph. After application of the modeling activity, students were evaluated based on their performance in solving the mathematical modeling questions and almost all were found to be successful. The researchers offered some recommendations through their experiences for teachers. Among these recommendations are that every student should present their mathematical model to class and discuss it with other students.