The effects of dietary rosemary extract supplementation in dairy ewes on milk performances and blood parameters were studied. Thirty-six pluriparous Valle del Belice ewes, organically managed, were divided into 3 homogeneous groups supplemented with 0 (CTR group), 600 mg (ROXLD group) and 1200 mg (ROXHD group) of rosemary extract per day per ewe. Rosemary extract was administered from parturition (Day 0) to 150 days of lactation. Rosemary extract affected milk yield (CTR = ROXLD < ROXHD; P < 0.001), the daily quantitative production of protein and casein (CTR = ROXLD < ROXHD; P < 0.01), lactose (CTR = ROXLD < ROXHD; P < 0.001) and fat (ROXLD < CTR < ROXHD; P < 0.001). blood concentrations of glucose (CTR < ROXHD < ROXLD; P < 0.05), non esterified fatty acids (ROXLD < ROXHD < CTR; P < 0.05), beta-hydroxybutyrate (CUR < ROXLD = ROXHD; P < 0.001), total protein (CTR < ROXLD = ROXHD; P < 0.001) and creatinine (CTR < ROXHD < ROXLD; P < 0.05); the activities of aspartate aminotransferase and alanine aminotransferase (CTR = ROXHD < ROXLD; P < 0.001), alkaline phosphatase (ROXHD = ROXLD < CTR; P < 0.001) and creatin kinase (CTR < ROXHD < ROXLD; P < 0.01). Finally, considering bone and mineral metabolism, the serum levels of inorganic phosphorus (CTR < ROXLD = ROXHD; P < 0.05) and calcium (CTR < ROXHD < ROXLD; P < 0.001) were significantly influenced by the dietary supplementation of rosemary extracts. Rosmarinus officinalis, thanks to its "natural functional ingredients" affects milk positively and alleviates the stress associated with lactation in animals; it could also represent a valid feeding strategy to ensure quality of the organic production.