The main purpose of this study was to assess the effects of doodling on learning performance of high school male students in Tehran. The design of this research was a pre-test–post-test with a control group. A group of 175 junior high school 12 -13 year old students was chosen for this study. After being taught a section of Natural Science course, the students were asked to answer questions related to the lessons. After that, their grades were used as the pre-test scores. The post-test was carried out after the devised treatment. During ten sessions of the same course and teacher, the students were given a blank sheet and were asked for doodling if they liked to/felt for. After each session, a couple of relevant written questions were asked to evaluate how well students learned the lessons. The experiment and control group both consisted of 27 randomly selected students; participants in experiment group were doodlers and those in control group didn’t doodle. To evaluate the doodling effect, covariance analysis is performed. Comparison of the grades showed that the experiment group outperformed the control group significantly (P<0.01).