Watermelon (Citrullus lanatus) is a highly valued fruit of the family of Cucurbitaceae and is cultivated and marketed in Benin for its watery flesh. It is a favorite fruit widely appreciated by many consumers, but few studies have been carried out to understand how its market is structured, how efficient it is and also how far it provides returns to stakeholders in the country. This study aims at evaluating the marketing efficiency of watermelon in Benin and assessing relationships between intermediaries involved in the fruit trade from production to consumption. A survey was conducted and included all the 195 traders registered in Benin during a census in 2015. The results showed that Kaolack and Sugar baby are the most traded cultivars in Benin. The fruit size, the sugar content and the color of the pulp are the main traits that trigger consumers’ choice. Four marketing channels were identified: a short one that involves one intermediary and a long one with three intermediaries between the producer and the consumer. The watermelon trade is efficient and provides a net marketing profit of 20 FCFA. (0.03 euro)/kg or 70 FCFA (0.11 euro)/fruit for a wholesaler while the retailers earn 50 FCFA (0.08 euro)/kg or 160 FCFA (0.24 euro)/fruit due to the fact that the transaction cost incurred by wholesalers is significant. The average marketing efficiency was estimated at 65%. Retailers are the most efficient with an efficiency rate of 70% while the wholesalers have 50% efficient rate. Nevertheless, only wholesalers earn a significant monthly revenue. We conclude that improving the trade efficiency of watermelon in Benin implies reducing the transaction costs.