The paper analyzes changes in magnetic declination in the Adriatic Sea from the first measurements in 1806 to the latest isogonic charts from 1995. The basis of analysis are data provided by the Adriatic pilot books as literature that mariners used as an indispensable instrument in sailing that has not been properly evaluated in the scientific research so far. It is emphasized the the magnetic declination was relevant primarily to overseas ferries, and was less important in coastal navigation, usually along the archipelagos of the eastern Adriatic maritime zone as terrestrial navigation was used in sailing in this belt with over a thousand islands and islets.