Background: The aim of this study was to examine the effect of volunteering for Special Olympics Games (SOG) on the attitudes of volunteers towards inclusion of people with intellectual disabilities. Method: A repeated measures design with 3-week follow-up was used. There were 100 volunteers recruited for the study and 90 of them completed the study. Results: It was revealed that a 1-week exposure to the SOG improved volunteers' attitudes towards inclusion of people with intellectual disabilities significantly (P = 0.016). Females had more positive attitudes than males at all three time points of measures. The interaction effect of gender was not significant. Conclusions: A 1-week exposure to the SOG can enhance volunteers' positive attitudes towards inclusion of people with intellectual disabilities and this effect can maintain for up to a month.