Milk fever is a condition in which an animal's body fails to maintain calcium homeostasis as a result of an increase in calcium demand during pregnancy or lactation. The clinical care of probable milk fever with the retained placenta in a Friesian cow following twin calves was described in this case. The principal complaint of a four-year-old Holstein Friesian cow weighing 450 kg was weakness and inability to stand a day after the birth of two calves. The cow was found to be in sternal recumbency and unable to stand, with the placenta hanging from the vulva region. The cow's vital signs were all normal, but she had a weak heartbeat. Milk fever, downers' cow syndrome, and hypophosphatemia were the differential diagnosis at the time. Based on the history of parturition of two calves and thus hypocalcemia, the cow was diagnosed with probable milk fever. Flunixin meglumine 1.1 mg/kg was given intravenously to the cow as an anti-inflammatory, anti-pyrexia, and analgesic. Then, as a calcium supply, 500 mL of calcium borogluconate (23%) was slowly supplied intravenously at a rate of 1 drop/second. After 10 minutes, the cow responded to the treatment. In addition, the retained placenta was irrigated with 0.9% normal saline lavaged into the uterus. As a last lavage, 20 mL of oxytetracycline (20 mg/kg) was injected into the uterine body. Finally, to avoid additional bacterial infections, a broad range long-acting oxytetracycline (20 mg/kg) antibiotic was given intramuscularly once. During the treatment of milk fever, the major focus should be on therapeutic treatment to restore the calcium level in the blood.