Severe combined immunodeficiency (SCID) is a primary inherited immunodeficiency that could be fatal, usually due to opportunistic infections caused by bacteria, viruses, fungi, and protozoa if left untreated. Opportunistic infections are the most common presentation of SCID these include viral, fungal, or intracellular bacteria, and infection should prompt immunological investigation. This review aimed to provide a comprehensive approach to the microrganisms associated with severe combined immunodeficiency (SCID) and its management. The authors described SCID as a syndrome and summarized the different microorganisms that affect children and how they are managed.