Raw legume seeds are important source of protein and other nutrients for monogastric animals. However, these legume seeds include many kinds of anti-nutritive factors (ANF) such as trypsin and chymotrypsin inhibitors, lectins and tannins. Although these ANF vary by species, cultivation areas and harvesting methods, they play a role in decreasing the utilization of nutrients. The pig is a monogastric animal which is slightly tolerant to the ANF in raw legume seed. Nevertheless, the optimal use of legume seed as a pig feed necessitates a lowering of the toxicity in the raw seed until it is appropriate for incorporation in the feed. There are many methods to improve the utilization of nutrients in legume seed, such as breeding improvement, physical treatments (decortications, dehulling, milling and others), heat treatments (toasting, boiling, extrusion, streaming or autoclave), chelating substances for binding toxics, radiation and soaking. The choice of the treatment depends on the availability of facilities and economic considerations. This article reviews and discusses the nutrients in legume seeds and might offer an important information on legume seeds for pig feed to nutritionists.