Gaining the attention is the first key step to enhance learning. In Attention-Deficit/Hyperactivity Disorder (ADHD) as the most prevalent deficit in school age, the learners face some impairment in attention that requires appropriate intervention. An environment that embedded Pedagogical Agent in computer-assisted instruction (CAI) has been designed to support learning through gaining and guiding attention to relevant information for these students. This study investigated how much the presence of pedagogical agent can improve learning in ADHD students. The learning environment was integrated with a pedagogical agent, named Koosha, as a tutor and motivator. This study employed a pretest and posttest experimental design with a control group. The statistical population was 30 boy students with ADHD in primary school from the North of Iran. The participants were randomly assigned to work with either an agent presenting a multimedia program or without an agent in mathematics. The results (Analysis of covariance -ANCOVA) suggested that experimental and control groups show a significant difference in mathematics achievement. According to this research, using the pedagogical agent can enhance the learning of ADHD students; so it can be considered as a valid school-base intervention for these students.