The Tellervo dendrochronological software builds upon the Tree-Ring Data Standard (TRiDaS) to provide a tool for recording and managing all manner of dendrochronological data. However, Tellervo is especially useful for dendroarchaeological research. The traditional file formats used in dendrochronology—and by association the applications that use them—have very limited and nonstandard methods for recording rich information about dendro samples and their context. Such information is especially important in dendroarchaeological research to ensure accurate conclusions are made. Tellervo is described here in the context of research carried out as part of the excavations of the Theodosian Harbor at Yenikapı, Istanbul.