This paper provides the results of the dendrochronological analyses of seven wood samples from the Ottoman fortress of Seddulbahir on the Gallipoli Peninsula or Turkey. It concludes that the trees were cut in the late spring of 1656. The data collected allows the first building phase of the fortress to be securely dated. By bringing together the dendrochronological results with various archival records about the fortress, a more precise building chronology for the fortress can be reconstructed. The probable initial period of construction was between 1656 and 1661.