Background: Blood donation can save the lives of people who are in serious conditions thus it is a global concern of all societies. Objectives: Evaluating the knowledge, attitude and practice (KAP) of Saudi adult subjects toward blood donation in Riyadh City. Methods: A cross sectional community survey design was conducted among 500 adult Saudi subjects who were interviewed in shopping malls of Riyadh City during the period from May to July 2017. The questionnaire included interview regarding the demographics of respondents, knowledge, attitude and practice regarding blood donation. Results: All the participants had significant knowledge about their blood group and the importance of blood donation. Also, the majority of respondents had adequate knowledge about the most common site of blood donation, the specificity of blood groups and the dangerous of donation of subjects with infection. Also, a good knowledge was found among most of respondents regarding the time, the complications and the precautions of blood donation. The attitude and practice pattern of participants were good among most of the participants .The KAP was adequate among 71% of respondents regarding blood donation and there was a significant association between the respondents good KAP with young age, male gender and higher educational degree. Conclusion: The KAP of most of Saudi subjects was good and showed a high prevalence of blood donation among them with a favorable attitude to donate blood.