A 26-year-old woman 3 months post-partum was admitted to our hospital suffering from gross visual disturbance. Magnetic resonance imaging (MRI) revealed a pituitary mass, extending into the suprasellar cistern, with intense gadolinium enhancement. Lymphocytic hypophysitis (LHy) was suspected, and the patient received high dose methylprednisolone pulse therapy (HDMPT). Her visual disturbance was dramatically ameliorated on the first day following initiation of HDMPT, and MRI revealed marked mass reduction. Her pituitary function recovered 6 months after therapy. This case report suggests that HDMPT proved effective for mass reduction of severe LHy and could obviate the need for a useless surgery.