Congenital lipoid adrenal hyperplasia is a very rare and severe cause of adrenal insufficiency. It occurs due to a mutation of the steroidogenic acute regulatory protein (StAR), disrupting adrenal steroid biosynthesis. Here, we report a case of a three-week-old female infant with vomiting, failure to thrive, electrolyte imbalance, and generalized hyperpigmentation. The hormonal assay and genetic diagnosis confirmed a mutation in the StAR protein, leading to adrenal insufficiency. Appropriate replacement therapy resulted in the resolution of clinical and biochemical abnormalities. This case is being reported for its rare etiology and diagnostic clues. It can guide clinicians to keep adrenal insufficiency as a differential diagnosis in a neonate presenting with hyperpigmentation and electrolyte disturbance to save lives.