The crisis experienced from the water supply causes food production to be adversely affected in the agriculture sector, which is the biggest consumer of water. The deficit irrigation strategy ensures the continuity of food production as well as using water effectively. However, since the plant grown in this strategy is exposed to abiotic stress, it experiences significant yield and quality losses. For this reason, it is necessary to develop approaches to improve yield and quality losses of the plant grown with deficit irrigation. In this study, the physical and physiological properties and mineral content of curly lettuce (Lactuca sativa L. var. Crispa) grown by applying different rates of biochar to the soil (0%, 1%, 2%, 3%) with varying irrigation water levels (100%, 67%, 33%) researched. The study determined that decreasing irrigation water level decreased plant height, stem diameter, number of leaves, root wet and dry weights, plant weight, chlorophyll and leaf relative water contents, stomatal conductivity and N, P, K, Ca, Mg, Na, Fe, Cu, Mn and Zn contents of curly lettuce, while increasing the membrane damage index, but the physical and physiological properties and mineral content affecting the yield and quality of curly lettuce improved with increasing biochar rates. In the study, as a result of the emergence of the highest stress factor in irrigation at 33% level, it was observed that physical and physiological properties and mineral content of curly lettuce were affected at the highest level, and the dose of biochar, which managed the stress most effectively, was 3%. As a result, considering that biochar has an important potential to improve yield and quality losses of curly lettuce grown under deficit irrigation conditions, the use of biochar in the deficit irrigation regime were found to be recommendable.