Background: antibiotic misuse is a common problem around the world with special regard to developing countries. It could result in increased rate of infections and admission to hospitals, high treatment costs as well as increased mortality rates. Aim of the work: this study aimed toassess the general knowledge of community population in Saudi Arabia (KSA) regarding the adverse effects of antibiotics overuse. Patients and methods: this was across-sectional descriptive study conducted among 1700 Saudi adults from the period of February to June 2017. Respondents were interviewed and filled out a questionnaire that consisted of 3 parts the: first parts considered their demographics, the other parts regards the use of antibiotics and knowledge about their adverse effects. Results: the pattern of antibiotic use showed that 76.8% have recently used antibiotics. The major source of antibiotic use was pharmacist (46.5%) followed by physician (23.9%). About 71.7% used antibiotics for cold and cough and 61.8% used antibiotics for viral diseases. The level of knowledge toward excessive use of antibiotics was in adequate among 61% of respondents and was good among 39% of them. A significant correlation was detected between young age and good knowledge. Conclusion: there was a lack in the public knowledge regarding the adverse effects of antibiotic overuse among Saudi subjects. Educational programs may be performed to fill up the awareness gaps and enhance the knowledge thus decreasing the costs paid by health authorities to manage the adverse effects of antibiotics overuse.