Hypertensive encephalopathy is a life-threatening but potentially reversible neurological condition that results from sudden, severe elevation of blood pressure, leading to failure of cerebral autoregulation and vasogenic oedema. Headache is often the earliest and most prominent symptom and is a critical diagnostic clue, especially when associated with visual disturbances, confusion or seizures. While posterior reversible encephalopathy syndrome (PRES) is the most recognised radiological correlate, hypertensive encephalopathy encompasses a broader spectrum of cerebral involvement and may present without the classic imaging patterns. This chapter focuses on the case of a 42-year-old pregnant woman in her third trimester who presented with the sudden onset of severe headache and was ultimately diagnosed with hypertensive encephalopathy with features of PRES and overlapping reversible cerebral vasoconstriction syndrome (RCVS). Through this case, we explore the pathophysiological mechanisms, differential diagnosis—particularly in pregnancy—and the importance of early imaging including magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) and magnetic resonance venography (MRV). The role of the ophthalmic examination in supporting the diagnosis and identifying hypertensive retinopathy is also highlighted. Accurate and timely diagnosis is essential to prevent irreversible brain damage, and targeted management, including blood pressure control and seizure prophylaxis, can lead to full recovery. This chapter concludes with clinical pearls, key diagnostic steps and future directions for improving the recognition and management of this rare but important cause of secondary headaches.