Hemophilia A is a worldwide disorder of coagulation system. It is a male disorder, yet females with hemophilia are rarely seen in communities with high rate of consanguineous marriages. The abnormalities in factor VIII gene transfer as an X-linked pattern in the family, affects as many as one-third of patients who had no family history of abnormality and thus the occurrence of a sporadic mutation could be documented. Hemorrhagic symptoms usually correlate with the plasma level of factor VIII and comprise a wide range of hemorrhagic pictures, including from fatal spontaneous bleeding in the brain to ecchymosis of the skin. The coagulation study needs to differentiate between the two types of hemophilia A and B as well as the categorization of the disease severity. In the developing countries, due to limitations in diagnostic hemostasis facilities and a scant number of experts in the field, it is estimated that noticeable numbers of undiagnosed patients with hemophilia A exist. Occasionally, we encounter undiagnosed cases by general physicians while having hemorrhagic symptoms. The purpose of this review is to recap clinical and diagnostic parameters, pitfalls, and interpretation of coagulation assay in hemophilia A.A literature review was done in PubMed and Scopus medical search engines using the keywords “Hemophilia” and “Haemophilia”. A time limitation for the publication beyond 1995 and publication in the English language were considered. A total of 94 original articles and chapters of books was selected for the current review. Additionally, a comprehensive and up-to-date information on the clinical and laboratory features for the diagnosis of hemophilia is also presented.