Rice is an important component in the quest for food security in Benin, but its production remains low and thus needs to be optimized. This study estimated technical as well as allocative efficiency and identified the sources of the inefficiency of rice farmers in Benin, with specific focus on the departments of Mono and Couffo. The study used secondary data obtained from the Ministry of Agriculture, Livestock and Fisheries. The data covers 210 rice farmers evenly spread out within the departments of Mono and Couffo. The Cobb-Douglas production frontier method was used to measure the level of technical efficiency of farmers, while allocative efficiency was examined using the marginal product value method. The results reveal that the technical efficiency of producers is at 78%, and that there are therefore possibilities of increasing rice production. The sources of inefficiency are age, sex, the level of education and access to finance. The results also revealed the existence of allocative inefficiency in rice cultivation. Manpower is overused whereas other production factors such as seeds, pesticides, and fertilizer are underutilized. Allocative efficiency is explained by sex, age, the area sown, the type of crop, and access to finance. These results indicate that rice farmers in the departments of Mono and Couffo would benefit from adopting the best agricultural practices such as the use of fertilizer, agro-chemical products, and irrigation.