Barley straw is one of the crop residuals that can be used as building material. Straw is the plant structure between the root crown and the grain head. The internal structure of a single straw is tubular, tough, and efficient. It contains cellulose, hemicelluloses, lignin, and silica with high bending and tensile strength. The tube shape is inherently stable and, with a microscopically waxy coat, slightly hydrophobic. Bales are compressed masses of straw left over after harvest. Straw bale construction provides high comfort and enables home owners and building managers to reduce energy consumption for heating and cooling by about 80%. This chapter discusses the possibility of using barley straw as a building material. It focuses on four issues. First, it draws attention to the benefits of straw bale construction. Second, this chapter highlights some factors influencing the use of barley straw bales as building materials such as bales preparation in the field, bale dimensions, bale type, bale moisture content, bale density and tying systems of bales. Third, the systems of straw bale buildings such as load bearing and in-fill wall system are presented. Fourth, the use of earth plaster reinforced with barley straw is discussed.