Psoas abscess is rare, especially in the neonatal period. It may be primary or rarely secondary to extend on from adjacent structures or to bacteremia caused by distant cutaneous infections. Vague clinical presentation may lead to delayed diagnosis. Appropriate drainage is necessary in addition to antibiotic therapy. Here we present a neonate was admitted with subcutaneous abscesses on his wrist and ankle. Staphylococcus aureus was isolated from the drainage material and proper antibiotic treatment was begun. On the 7th day of treatment, he developed swelling on his groin and limited hip motion. Septic arthritis was suspected and a magnetic resonance imaging performed revealing an abscess on the right psoas muscle. Drainage and antibiotic treatment led to resolution of abscess. Development of multiple subcutaneous and deep abscesses in newborn period led us to suspect of primary immunodeficiency. In the immunological work up, serum immunoglobulins and lymphocyte sub set analysis were in normal ranges according to age. The phagocytic cell functions were tested with nitroblue-tetrazolium (NBT) slide test were also normal. Flow cytometry analyses revealed CD18 16%, CD11a + CD18 17%, CD11b + CD18 3%, CD11c + CD18 4%. A ratio of 1.89 oxidative explosion, 1.63 phagocytosis and 1.43 chemotaxis (N: >1.5) was determined in neutrophil function tests. Antibiotic prophylaxis was initiated and bone marrow transplantation was recommended. As a conclusion, immunodeficiency syndromes such as LAD should be investigated in newborn with psoas abscess. Our case is important to emphasize underlying factors in the pathogenesis of psoas abscess.