This study examines the relationship between the attitudes toward people with ID with religiosity, meaning in life and prosocial behavior among Hong Kong young adults. Religiosity, meaning in life and prosocial behaviour have been found with effect on individual beliefs, values and behaviors, but no conclusive result has been confirmed in the influence of these constructs on attitudes toward people with ID. The study used an online survey and adopted the 5-item Centrality of Religiosity Scale, the 16-item Prosocialness Scale for Adults, the 10-item Meaning in Life Questionnaire and the 16-item Attitudes to Disability Scale (ADS) to collect information from 543 samples in Hong Kong to explore the relationships between these variables. Among the samples, 33.3% are male while 66.7% are female, and the age of respondents is between 18 to 25. Results of the path analyses indicated that presence of meaning and search for meaning were mediators in the relationship between religiosity and attitudes toward people with ID. Religiosity was significantly related with presence of meaning, search for meaning and prosocial behaviour. Presence of meaning and search for meaning were significantly related with prosocial behaviour and attitudes toward people with ID. Moreover, prosocial behaviour was significantly related with attitudes toward people with ID. Based on the result, recommendations were made from various perspectives. To promote a positive attitude towards people with ID, it is suggested to incorporate service-learning opportunities in schools and organize an inclusion project for the public to promote the participation in social service to enhance the understanding and gain experience in contact with people with ID.