A shift has occurred in the diagnostic and therapeutic modalities considered for patients with primary immunodeficiency diseases (PIDs). Early diagnosis remains the mainstay in appropriate management and remarkably influences the prognosis. More specific diagnostic tests as well as therapeutic modalities have been introduced in the last few decades. Nonetheless, the importance of a thorough history taking and physical examination should not be neglected. Novel diagnostic modalities including genetic sequencing have led to the recognition of previously unknown defects underlying PIDs. In addition, newborn screening is being advocated as an imperative diagnostic test. In terms of treatment, hematopoietic stem cell transplantation is considered the optimal treatment modality for many cases and has dramatically improved the outcome. Gene transfer into hematopoietic stem cells prior to transplantation has improved the efficacy of hematopoietic stem cell transplantation. In this article, the latest advances made in terms of diagnosis and treatment of PIDs are reviewed.