||In the past, “Western” historical studies on Luso-Ottoman relations have been based on European sources and bibliographies; from seventies of the last century a new approach based on Ottoman archival sources had been undertaken through an examination of and comparison with the European sources. Unfortunately, Ottoman archival and chronicle materials are scarce with respect to the first siege of Diu and it is necessary to make use of European sources or, however, not in Ottoman language. It means that our major conclusions rest mainly on European sources (Italian, Portuguese etc.). The narrative of Lopo de Sousa Coutinho is part of that rich chronicle material in Portuguese with reference to the Luso-Ottoman relations and, in particular, to the siege of 1538, but historians have tended to neglect it. It is time that they take into Consideration this chronicle source.