Introduction: Solitary mastocytoma (SM) represents the most localized and benign form within the spectrum of mastocytosis. It is predominantly a paediatric condition and usually presents during infancy or early childhood. Congenital presentations are uncommon and may pose diagnostic challenges, particularly in distinguishing isolated cutaneous involvement from systemic mastocytosis. Accurate diagnosis is essential to guide management and avoid unnecessary invasive investigations. Case Report: A full-term male neonate, born at 38 weeks’ gestation with a birth weight of 2.95 kg, was admitted to the Neonatal Intensive Care Unit at District General Hospital, Ampara, following identification of a congenital abdominal nodule. On clinical examination, the infant was clinically stable, not pale, and had no significant hepatosplenomegaly or lymphadenopathy . No neurocutaneous abnormalities were observed; however, the lesion demonstrated a positive Da rier sign. Initial investigations, including abdominal ultrasonography , were normal. Serum tryptase level was mildly elevated at 12.5 ng/mL. In view of this finding, the infant was referred to the National Cancer Institute (Apeksha Hospital), Maharagama, for further evaluation. Bone marrow aspiration and histopathological assessment excluded systemic mastocytosis and confirmed localized cutaneous mast cell proliferation, consistent with a diagnosis of solitary mastocytoma. Discussion: This case underscores the importance of a structured diagnostic approach and multidisciplinary collaboration in the evaluation of congenital mast cell disorders. Early exclusion of systemic involvement allowed for conservative management and reassurance of the family , with an excellent prognosis expected.