The circumstances of the saga's composition are exceptionally well understood, as they are recorded in some detail in Sturlunga saga (particularly Sturlu þáttr): the saga was written in the 1260s (apparently 1264-65) by the Icelandic historian and chieftain Sturla Þórðarson (nephew of the noted historian Snorri Sturluson).
The saga is the main source to Norwegian history for the period from 1217 (Haakon's accession) to his death in 1263.