Some of the main characteristics of autism spectrum disorder (ASD) are difficulties in the domain of social communication and interaction. These difficulties can very often contribute to the formation of negative attitudes toward people within this population, which makes their general inclusion in society more difficult. In order to improve peers' attitudes toward people with ASD, inclusion of students with this diagnosis is nowadays implemented in mainstream schools. Previous research provides information on a number of factors, such as personal experiences with people with ASD and gender, that can influence attitudes toward people with this disorder. The aim of this research was to investigate the attitudes of early school-age children and their features toward their peers with ASD. The research was done by conducting Croatian translation of Children's Attitudes Toward Autism Questionnaire in two second grades of one and two third grades of another elementary school in Croatia. The questionnaire examined students' attitudes on all three components of attitudes; emotional, cognitive and behavioral. The participants in this research were 24 male and 45 female students. Students whose class includes a child with a diagnosis have more positive attitudes in general and on all components of attitudes than students whose class does not include a child with ASD. Students who had personal experience with ASD diagnosis have more positive attitudes on all components of attitudes, except behavioral, compared to students who had never had experience with people with this diagnosis. Gender differences in attitudes toward peers with ASD have not been found. The results of this research point out the positive effects of inclusion of children with ASD in mainstream schools in Croatia, which are reflected in more positive attitudes of students who attend a class with a student with this diagnosis compared to students from classes in which students with the same diagnosis are not included. Additionally, students with previous experience with people with ASD express more positive attitudes about them, which sends an important social message; the foundation of a society that respects diversity lies in exposure to all kinds of diversity from an early age.