In the Mantaro Valley and high Andean areas of Peru, the pastures are established without weed control or sowed with companion crops (Barley). The sowing of the peas with pastures can mean greater productive advantages. The objective was to determine the establishment of an association of grasses and legumes sowed with densities of peas (Pisun sativum L.) cv "Remate" in the Mantaro valley, Peru. The study was conducted in IVITA (Veterinary Institute of Tropical and Height Research). The Mantaro valley is located at 3320 meters above sea level. The densities of the peas were 0.0; 25.0; 50.0 and 75.0 kg. ha-1, sowed on the ground with 28.0 kg. ha-1 of total seed of the pasture: 20.0 kg. ha-1 Italian Ryegrass (Lolium multiflorum) cv "Tama"; 4.0 kg. ha-1 of red clover (Trifolium pratense) cv "Quiñequeli" and 4.0 kg. ha-1 of alfalfa (Medicago sativa) cv "SW8210". We used Random Block Design with 3 repetitions. The response variables were botanical composition (%) and dry matter production (kg. ha-1). A good establishment result sowing 28.0 kg. ha-1 of pasture associated with 50.0 kg. ha-1 of peas, expressed in percentages higher than 90% in the botanical composition and reasonable productions of dry matter. (DM).