BackgroundGlobal evidence has linked unused medications and their inappropriate disposal to adverse health, economic, environmental, and ethical impacts. However, such evidence is scarce in Qatar. This study explored patients’ knowledge and attitude toward unused medications and their practices toward medication supply and disposal (KAP) in Qatar. Materials and Methods:Study designA cross-sectional survey using a pretested questionnaire was done between February 2020 - October 2020. Descriptive statistics, Man Whitney U, and Kruskal–Wallis Rank-Sum tests were applied. Chi square test assessed the association between socio-demographic characteristics and KAP scores. Characteristics that were found significantly associated with KAP (i.e., p-values <0.05) were further included as predictor variables in the multiple linear regression model. ResultsAll items pertaining to patients’ Knowledge were found good (Mean score 3), except regarding that of “awareness of unwanted medication return policy” (Mean score 3), i.e., the lowest level of patients’ agreement (31%) (Median (M) = 3, Interquartile Range (IQR) = 3). Their attitude was generally good (Mean score 3). Conversely, their practice toward medication supply was bad (Mean score 3). Possible future use was the most reported reason (79%) for keeping medications at home and trash was the most widely disposing place of unused ones (76%). Knowledge was significantly higher among non-laborers and other occupations than patients with no work (p < 0.001) and (p = 0.005), respectively. Attitude was significantly lower among patients with healthcare providers (HCPs) in their household than those without (p = 0.001). Practices were also significantly lower among those aged 40–49 years and those with HCPs in their household than those aged 18–29 years (p = 0.012) and those without HCPs, (p < 0.001), respectively. ConclusionsOverall, patients’ knowledge and attitude toward unused medications seem good while their practices toward medication supply and disposal is bad. To mitigate health, economic, and environmental impacts of unused medications, interventions including rationalizing drug supply, use, disposal, prescribing, manufacturing, and promotion are recommended.