Despite the fact that Mexico has vast biocultural biodiversity, there are numerous regions where the traditional medicinal use of plants has not yet been studied. We aimed to document, analyze quantitatively, and preserve medicinal plant knowledge among local people living in over 40 communities in the state of Zacatecas. Ethnobotanical information was collected by semistructured interviews with 132 informants. Data were analyzed using standard quantitative indices such as relative frequency of citation, family importance value, cultural importance index, and informant consensus factor. We recorded 168 medicinal plant taxa belonging to 151 genera and 69 botanical families and used to treat 99 health disorders. The most medicinally important plant families were Asteraceae (20 species), followed by Fabaceae and Lamiaceae (12 species) and Cactaceae (five species). The most culturally important species was Matricaria chamomilla L., mentioned 140 times, followed by Arnica montana L. (62 times) and Artemisia ludoviciana Nutt (48 times). The highest consensus for use was for diseases of the reproductive system. The type of disorder for which there was the highest number of references for use (389; 25% of all uses) and plant species (67) were diseases of the digestive and gastrointestinal system. The present study represents the first quantitative medical-ethnobotanical documentation and analysis of the traditional use of medicinal plants in Zacatecas state. Despite the semiarid climate, this region is botanically highly diverse, and its flora have versatile medicinal uses.