Background: Down syndrome (DS) is commonly associated with complex respiratory phenotypes due to anatomical, immunological, and vascular factors. Pulmonary sequestration (PS) is a rare congenital malformation of non-functioning lung tissue with anomalous systemic arterial supply, occasionally reported in syndromic individuals. Case presentation: We report the case of a female infant with DS who developed acute respiratory distress secondary to respiratory syncytial virus infection. Chest imaging revealed an intralobar pulmonary pseudosequestration in the right lower lobe, supplied by the celiac trunk and draining into the pulmonary veins, with a communication to the bronchial tree. The patient required pediatric intensive care support and nutritional rehabilitation. Surgical resection was deferred until adequate weight optimization could be achieved. Discussion: This is, to our knowledge, the first description of intralobar pulmonary pseudosequestration in a patient with DS. The association suggests possible overlapping developmental mechanisms involving abnormal angiogenesis and emphasizes the importance of considering congenital pulmonary malformations in DS patients presenting with recurrent or severe respiratory symptoms. Conclusions: Early recognition and tailored management may improve clinical outcomes in this vulnerable population.