Background: Self-Medication is an increasingly frequent worldwide health problem especially in developing countries like Egypt. Some studies suggest that there is a relationship with socioeconomic (SES) and environmental factors. Objective: This study aimed to describe the prevalence, pattern, possible etiological factors and reasons of self- medication among adults attending two private pharmacies from different regions (slum and urban) with different socioeconomic and environmental status in Cairo, Egypt. Methodology: This is a cross-sectional study carried out from September to December2020; a random sample of 150 adults completed a predesigned self- administered interview questionnaire on self-medication practices. Results: a majority of participants practiced self-medication with a prevalence rate (73.4%). Common cold, headache, cough and gastrointestinal diseases were the most common illnesses among adults opting for self-medication (SM) and they tended to select SM if the illness was minor. Residence and family expenses were the independent determinant variables in socioeconomic status significantly affecting the practice of self-medication. Conclusion: the prevalence of self-medication with medicines is high among adults in urban and slum areas of Cairo, Egypt that needs intervention. Recommendation: further studies need to be done in order to extend this study outside the capital city; Cairo to include other cities, slum and rural areas in Egypt.