The purpose of this study was to investigate the efficacy of cooperative teaching method on the attitude and academic achievement of the fifth-grade students in mathematics in Gachsaran city. 93 girl and boy students who were randomly selected fell into two groups of control and experimental where in the latter students experienced cooperative teaching method. Each group took a pretest and posttest. Pretest measured their Math achievement ability and their attitude to mathematics. After the treatment was carried out in the experimental group, the data in both groups were analyzed. Data analysis indicated that mean score of the experimental group was significantly more than that of control group. Also, the scores of the attitude survey showed a significant difference in experimental group. Furthermore, although mean score of the boys is more than that of girls, it is not significant. The research results showed that although using cooperative teaching method, rather than traditional method, was significantly more effective and increased the positive attitude of the students to study mathematics, it was not significant regarding the variable of gender.