The purpose of this study is to investigate the effects of brain teasers on attention spans of preschool children of age six. The study was conducted using an experimental design with a control group and pre-test/post-test. The sample of the study is children of age six selected via random appointment among ones who were enrolled in the Merkez Kindergarten in the province of Sivas, district of Sarkisla in the school year 2014-2015. The sample consists of a total of 213 participants including 113 in the experiment group and 100 in the control group. "Frankfurter Tests für Fünjahlige-Konzentration" was used as the measurement tool. The experiment group was given the brain teaser curriculum 3 days a week, one hour a day for 10 weeks, while the control group was given only the National Education Ministry Pre-School curriculum. The obtained data were organized and analyzed using the SPSS 22 (Statistical Package for the Social Sciences) package software. Dependent samples t-test was used in order to analyze the differences between the experiment and control groups, while percentages, frequencies and means were used for demographics. As a result of the study, it was seen that there was a significant difference in favor of the experiment group between the attention spans of children who received the brain teasers curriculum and children who received the National Education Ministry Pre-School curriculum. This result shows that brain teasers are effective in improving the attention span.