Helgafell was an important farm in western Iceland in the medieval period. A sediment core was taken from Helgafellsvatn, its watershed encapsulated by the farm boundary. Using sedimentary and palynological data derived from the core, the aim of this study is to evaluate the palaeoecological record of Helgafell from Landnám (ca. AD 877) until AD 1300. In particular, to understand land use associated with the farm in relation to livestock, erosion and vegetation. Within a wider context, palaeoecological data from the pre-Landnám period are also considered, as is the foundation of a monastery at Helgafell in the late 12th century. The chronological framework is built upon tephrochronology, 14C and Pu dating. Prior to Landnám, Betula has a strong presence with further developments in the vegetation inferring a climate amelioration in the period ca. AD 500–900. This is followed by Landnám and the development of a pastoral landscape. There is also some evidence for the introduction of plants with utilitarian applications. The founding of Helgafellsklaustur does not result in a strong ecological or environmental signal. A particular feature of the palaeoecological record for Helgafell is the stability in environmental conditions despite the presence of livestock. A number of factors may be contributing to this phenomenon, including a distal location from windborne sources of minerogenic material, mild coastal temperatures, and the easing of grazing pressure via transhumance.