Northern Peru is the center of the so-called Andean “health axis,” where the continuous use of more than 500 medicinal plants has been documented. Local healers as well as patients purchase a large portion of their plants at local markets. While scientific studies of medicinal plants are under way, concern has arisen over the preservation of both the large diversity of medicinal plants and the traditional knowledge of healing methods that accompanies them. To promote further conservation work, this study attempted to document the sources of the most popular and rarest medicinal plants sold at the markets of Trujillo (Mayorista and Hermelinda) and Chiclayo (Modelo and Moshoqueque), as well as to create an inventory of the plants sold in these markets. The present paper reports on the complete market flow from collection to middlemen to vendor from the perspective of an herb collector/vendor. Although prior studies have indicated that at least some plants, mostly introduced species, are grown in home gardens on the coast, this study shows that increasing plant demand in the large coastal markets has not led to significant cultivation of medicinal plants in home gardens. The vast bulk of the plant material sold in the markets of northern Peru consists of plants collected in the wild. Both collection of plants and their transport to the coastal markets require long-distance travel. Low profit margins indicate that the herb trade is very fragile, since collectors might decide to engage in activities that offer higher income or higher turnover. This, coupled with the fact that most plant material is wild-crafted, could easily lead to overharvesting of rare medicinal species in the region.