Sub-diaphragmatic extralobar pulmonary sequestration (PS) is an extremely rare malformation defined as a portion of lung tissue that is totally discontinuous from the tracheobronchial tree and usually has its own pleural covering with an anomalous systemic blood supply. It is usually associated with other congenital malformations. The authors present an extremely rare case of isolated sub-diaphragmatic PS which was antenatally detected and followed up with postnatal ultrasound, where it masqueraded as a suprarenal mass; it was totally asymptomatic with spontaneous resolution at age of two years. This case emphasizes to add a differential diagnosis of malformation in congenital supra-renal masses, which remain stable in size and appearance, with possible spontaneous resolution and hence avoid immediate intervention and surgery.