BackgroundNon-prescribed antimicrobial use and their resistance are among the main public health problems, worldwide. In Ethiopia, particularly in the northern part, the magnitude of non-prescribed antimicrobial use and its major determinants is not yet well known. Thus, this study was done to assess the magnitude of non-prescribed anti-microbial use and associated factors among customers in drug retail outlet in Central Zone, Tigray, Ethiopia.MethodsA drug retail outlet based cross-sectional study was conducted among adults aged 18 years and above. A multistage sampling procedure was used to select study participants. Data were collected using a structured questionnaire by druggists under the supervision of pharmacists. Data were entered into EpiInfo software version 3.5.4. Binary logistic regression was used to identify independently associated variables in bivariate and multivariable analyses using SPSS version 21. Odds Ratios with 95% confidence intervals were estimated.ResultsFrom 829 study samples, a total of 780 respondents participated in this study with a response rate of 94.1%. Of 367 respondents who received non-prescribed antimicrobial, 249 (67.8%), 121 (33%), and 94 (25.6%) of them were males, secondary school and paid employed respectively. The magnitude of non-prescribed antimicrobial use was 47.1% (95% CI: 43.8, 50.5). The factors which were independently associated with non-prescribed antimicrobial use were male sex [AOR = 1.72, 95% CI = 1.21, 2.44], seeking modern health care in private/Non-Governmental Organization (NGO) [AOR =0.47, 95% CI; 0.23, 0.98], moderate waiting time in health care facilities [AOR = 1.92, 95% CI; 1.20, 3.09], delayed waiting time in health care facilities [AOR = 1.56, 95% CI; 1.03, 2.38], ever received antimicrobial [AOR = 3.51, 95% CI; 2.45, 5.02], and frequency of purchasing non-prescribed antimicrobial (1–3 times and 4 times, [AOR = 2.04, 95% CI; 1.36, 3.06] and [AOR = 2.66, 95% CI; 1.24, 5.68] respectively).ConclusionThe magnitude of non-prescribed antimicrobial use was high. Familiarizing with health care utilization and delayed waiting time in health care facilities were the very important factors independently associated with non-prescribed antimicrobial use. Emphasis should be given to community education through involvement of the private health sector and health care providers. Regulation and policy enforcement are also necessary to promote the rational use of antimicrobial.