The aim of this study is to investigate the efficiency of cooperative learning on preschoolers' verbal mathematics problem-solving abilities and to present the observational findings of the related processes and the teachers' perspectives about the application of the program. Two experimental groups and one control group participated in the study. Results found that preschoolers in the experimental groups experienced larger improvements in their problem-solving abilities than those in the control group. Findings also revealed that the cooperative learning method can be successfully applied in teaching verbal mathematics problem-solving skills during the preschool period. The preschoolers' skills regarding cooperation, sharing, listening to the speaker and fulfilling individual responsibilities in group work improved. The teachers' points of view also supported these findings.