BackgroundAntimicrobial Resistance (AMR) is a major global concern. Irrational use of antibiotics including self-medication (SM) with leftovers without a medical prescription can be a leading cause. This study aimed to investigate the prevalence and related factors of leftover antibiotics (LA) in Lebanese households. Study designA cross-sectional study of the Lebanese population was conducted between March and October 2022. MethodsThrough random proportional stratified sampling, a total of 494 families participated in this study. Data collection was carried out through phone calls using a comprehensive and reviewed questionnaire. The data was then analyzed using SPSS version 26. Logistic regression was utilized to identify the factors associated with LA, with the presence of LA in households as the dependent variable and other factors such as age, region of residence, and presence of elderly individuals at home as the independent variables. ResultsAmong selected households, 118 households (23.89%) had LA. The most common type of antibiotic found was penicillin (59.84%). Most of the LA were in the form of tablets and capsules (94%) with valid expiration dates (87%). Antibiotics were mainly prescribed by doctors (61%), and the main reason for prescribing was acute respiratory tract infections (47.46%). SM was reported by 42.37% of the families with LA. A family with elderly patients (p = 0.002; OR = 2.23; 95% CI = 1.33–3.73) and those residing in Mount Lebanon (p = 0.019; OR = 2.28; 95% CI = 1.14–4.56) had significantly higher odds of having LA. ConclusionLeftover antibiotics were found in nearly a quarter of the addressed Lebanese families. Therefore, public educational campaigns should be launched to limit injudicious antibiotic use including SM, and to promote proper disposal of any leftovers. It is also crucial to adopt the One Health approach by developing national programs for the safe disposal of LA and implementing regulations to restrict the distribution of antibiotics in pharmacies without a prescription.