In 1273, when he was 5 years old, he was given the title of king, alongside his father, who planned to hold a coronation for Eirik as his subordinate co-ruler in the summer of 1280.

During his minority, the kingdom was ruled by a royal council consisting of prominent barons and probably also his mother, the dowager queen Ingeborg.

[3] Eirik briefly and unsuccessfully laid claim to the Scottish crown as inheritance from his daughter.

In 1287, he entered into an alliance with a group of Danish nobles, most prominently Jacob Nielsen, Count of Halland and Stig Andersen Hvide, who were outlawed in Denmark for allegedly murdering the Danish king Eric V. Eirik gave the outlaws sanctuary in Norway in 1287.

King Eirik himself led a large Norwegian fleet which, along with the Danish outlaws, attacked Denmark in 1289, burning Elsinore and threatening Copenhagen.