Fat supplements are fed to lactating dairy ewes to increase the energy density of the diet, increasing milk yield and milk fat content and yield. However, studies using lipid supplements with higher content of saturated fat and its effects in lactating ewes are still not fully understood. This study evaluated the effects of a lipid supplement rich in stearic acid (C18:0, 88%) fed to Lacaune lactating ewes, on milk production and composition. Thirty-two lactating ewes (122 DIM) were used in a completely randomized design for 21d (7d of adaptation and 14d of measurements), receiving the following treatments: Control (corn silage + 1 kg of concentrate - DM basis) and C18:0 (corn silage + 1 kg of concentrate - DM + 32 g/d of C18:0). The C18:0 was mixed to the concentrate and fed individually. Milk yield was measured individually and milk samples were taken every 2d. Data for milk yield and composition were analyzed as repeated measures using the PROC MIXED of SAS, assuming the treatment as a fixed effect. The data for milk yield and composition from d0 (day zero) collected just before starting the experiment was used as a covariate in the model. Compared with Control, respectively, the C18:0 increased milk fat content by 4.4% (P = 0.02) and decreased lactose content by 3.8% (P = 0.001). The C18:0 also decreased milk yield by 8.5% (P = 0.05), fat and lactose yield in 8.5 and 3.5% (P = 0.04), respectively. Overall, our results showed that C18:0 was able to increase the milk fat content and decrease milk fat yield as a consequence of a reduced milk yield in lactating ewes at late lactation.