: Torcular dural sinus malformations (tDSMs) are rare congenital defects representing a complex of vascular anomalies that have been grouped in one single unit. Although the current literature suggests a generally favourable prognosis for prenatally diagnosed tDSMs, there are still only limited data and published papers on the subject. Factors resulting in an adverse outcome of the fetuses and children have to be taken into consideration to determine precisely the nature of the consultation and management. A 33-year-old primipara at 21 weeks, 5 days of gestation was referred to our clinic with the suspicion of a central nervous system (CNS) malformation of the fetus, and the diagnosis of tDSM with thrombus was made. No factors contributing to an adverse outcome such as arterialization of the lesion, ventriculomegaly or neuroparenchymal damage were present. The pregnant woman was scheduled for regular sonographic and magnetic resonance imaging (MRI) controls. In the third trimester the lesion decreased in size, which is a key imaging marker for a favourable prognosis. The child was born in term, and the latest neurological examination at the age of six weeks is without pathological findings. This case study demonstrates a prenatally diagnosed tDSM with a favourable outcome with a regression in the size of the lesion during the prenatal period.