Drug addiction is one of the alarming public health and social problems in Afghanistan and around the world. Addiction denotes the habitual use or the physical or mental dependence on narcotic drugs or psychotropic substances.Drug addicts who were admitted to six public addicts' rehabilitation centers in Herat, Afghanistan between March and July 2019 were recruited for this descriptive study. A total of 299 drug addicts were included in this study. A 77-item questionnaire containing three subscales: 39 items for personal information, 32 items for drug use, and 6 items for dependence and treatment subscale were validated and used for data collection. IBM SPSS Statistics for Windows v.22.0 was used for data analyses.The median age of the participants was 30 years. Of all participants, 79.1% were male, 56.6% were illiterate, and 1.7% were university graduates. In this study, 44.8% of the participants used heroin, 20.7% used opium and 15.4% used methamphetamine. Almost half of the participants (49.5%) declared that at least one member of their families was a drug user. Of the 299 drug users included in this study, 64.9% stated that at least one person close to them (except family members) used drugs. Over two-thirds of the participants (78.4%) had easy access to drugs, 26.8% had broken laws for money/drugs at least once.This study revealed that male illiterate teenagers living in low-economic nuclear families were more vulnerable to drug use in Herat, Afghanistan. The most common reasons for drug use were curiosity, peer influence, and seeking pleasure.