There is limited information on periodic markets for environmental products. This paper uses the case of medicinal plant periodic markets in Nepal to empirically develop typologies of periodic markets and the retailers operating there, while also estimating the economic importance of such markets. Data were collected on the structure and functions of periodic markets (n = 55) in Morang District in Southern Nepal through structured medicinal plant retailer interviews (n = 57), semi-structured key informant discussions, recording of daily transactions in individual medicinal plant stalls (n = 9), and direct observations of market characteristics. The study identified: (i) three types of markets (high, medium, and low order markets), characterized by nine factors: location, accessibility, physical layout, size, infrastructure, variety of products, governance, retailer types, and range of retailers and (ii) two types of medicinal plant retailers which were further divided into four sub-types and eight specific types. Periodic market trade included 60 medicinal plant products with an annual volume of 30 tonnes, equivalent to 10% of out-of-district exports. Due to high retail unit prices, however, the annual value of USD PPP 0.48 million is equivalent to the out-of-district export value indicating that local retail trade of medicinal plants in periodic markets is of substantial importance and can be used to enhance access to local health care and supporting rural livelihood through increased cash incomes.