During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, Helgøy Municipality was merged back into Karlsøy Municipality. At the same time, all of the mainland areas of Karlsøy (the northern part of the Lyngen peninsula, with 1,001 inhabitants) was transferred from Karlsøy to neighboring Lyngen Municipality. After all the changes, the new Karlsøy had 3,414 residents. On 1 January 2008, the southern part of the island of Reinøya was transferred from Tromsø Municipality to Karlsøy Municipality.
During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964 Helgøy Municipality was merged back into Karlsøy Municipality. At the same time, all of the mainland areas of Karlsøy (the northern part of the Lyngen peninsula, with 1,001 inhabitants) was transferred from Karlsøy to neighboring Lyngen Municipality. After all the changes, the new Karlsøy had 3,414 residents. On 1 January 2008, the southern part of the island of Reinøya was transferred from Tromsø Municipality to Karlsøy Municipality.