The present study was conducted to collect, record, and document local knowledge of medicinal practices in Duzce, a northwestern Anatolian province. To the best of our knowledge, no comprehensive ethnobotanical study has been reported from this province. Information was acquired through semistructured interviews and personal conversations using a questionnaire and numerous guided field trips with local knowledgeable people. For quantitative analyses and comparisons, recorded data such as informant consensus factor (F-IC) and use value (UV) were calculated, respectively. As a result of extensive field studies, 122 taxa were determined as folk medicines; 76 of were wild and 46 were cultivated. The identified medicinal plants were mainly from the family Rosaceae, followed by Compositae, Apiaceae, Lamiaceae, and Solanaceae, respectively. Among the preparations used, liquid forms such as infusions (30.2%) or decoctions (16.4%) represented the most favored ways to administer medicinal plants. Dermatological disorders had the highest F-IC score with a value of 0.75 followed by skeletomuscular (F-IC = 0.7466), gastrointestinal (F-IC = 0.6666), immunological (F-IC = 0.6615), and respiratory (F-IC = 0.6292) system disorders, among others. The most prominent medicinal plants were Urtica dioica (UV = 0.4352), Plantago major (UV = 0.3056), Rubus ulmifolius (UV = 0.2279), and Sambucus ebulus (UV = 0.2279). According to the present study, the number of people who recognize and use the wild plants of Duzce, and those of the rest of Anatolia, is steadily decreasing. The ethnobotanical knowledge cannot be passed to the next generation in its entirety if it is not properly recorded. In addition to this gradual loss of knowledge, modern information pollution and contamination via the popular media highlight the urgent need to record this precious knowledge before it is lost.