This paper presents the results of a palaeoenvironmental investigation of riverine deposits containing charred heathland plant material, recovered during an archaeological survey of Gleann Mor Barabhais, Lewis, Western Isles of Scotland. This survey was conducted to identify Mesolithic occupation in the interior of the island and was undertaken as part of a wider project investigating the Mesolithic of the Western Isles. The recovery of carbonised material of Mesolithic date is discussed in light of the long-standing debate on detecting hunter-gatherer impact on environments using palaeoenvironmental records. The findings are compared to regional pollen sequences, where peaks in micro-charcoal levels and associated reductions in arboreal pollen are interpreted as evidence for anthropogenic fire ecology. These have been identified in areas where archaeological evidence for human occupation is absent. It is argued that this site reflects deliberate burning of vegetation by humans, most likely a small hearth, and therefore represents the first direct inferred evidence for the Mesolithic in the interior of the Western Isles.