Arterial hypertension in young adults, which includes patients between 19 and 40 years of age, has been increasing in recent years and is associated with a significantly higher risk of target organ damage and short-term mortality. It has been reported that up to 10% of these cases are due to a potentially reversible secondary cause, mainly of endocrine (primary aldosteronism, Cushing’s syndrome, and pheochromocytoma/paraganglioma), renal (renovascular hypertension due to fibromuscular dysplasia and renal parenchymal disease), or cardiac (coarctation of the aorta) origin. It is recommended to rule out a secondary cause of high blood pressure (BP) in those patients with early onset of grade 2 or 3 hypertension, acute worsening of previously controlled hypertension, resistant hypertension, hypertensive emergency, severe target organ damage disproportionate to the grade of hypertension, or in the face of clinical or biochemical characteristics suggestive of a secondary cause of hypertension. The 2023 Guideline of the European Society of Hypertension recommends starting pharmacological therapy from grade 1 hypertension (BP ≥140/90 mm Hg), with the aim of achieving BP control of less than 130/80 mm Hg. It is important to highlight that the prevalence of secondary hypertension in these patients could be underestimated, given that there is little evidence available on the management of high BP in young adults, which is why we developed this narrative review on the diagnostic and therapeutic approach to the major secondary causes of arterial hypertension in young adults.