This study aimed to determine whether the addition of a microencapsulated herbal blend (MHB) based on thymol, carvacrol, and cinnamaldehyde in dairy sheep feed would improve production efficiency, milk quality, and animal health. Thirty lactating Lacaune ewes were divided into three groups: Control (T0), 150 mg blend/kg of feed (T150), and 250 mg blend/kg of feed (T250). Milk was measured before the beginning of the experiment (d 0), at the end of the adaptation period (d 15), and during the experiment (d 20). In milk samples, was measured the composition, somatic cell count (SCC), reactive oxygen species (ROS), lipoperoxidation (LPO), and total antioxidant capacity. The MHB improved the milk production (only T150 vs. T0 sheep on d 20), productive efficiency and feed efficiency, and reduced the milk SCC (only T250 vs. T0 sheep, on d 20), ROS and tended to reduce the milk levels of LPO (only T250 vs. T0 sheep on d 20). Also, MHB reduced the blood levels of neutrophils and ROS (only T250 vs. T0 sheep on d 20) and increased total protein and globulin levels. Thus, a microencapsulated blend of thymol, carvacrol, and cinnamaldehyde improved the productive performance and milk quality of sheep.