As with other hills of the Cuillin, a head for heights and scrambling ability are needed to attain the summit. The least technical route follows a feature known as the "Great Stone Chute", a scree gully that leads up from the corrie of Coire Lagan to a col just below the main ridge. From this col, a pleasant scramble (Grade 2 standard) up the well scratched east ridge leads to the narrow summit.
Other routes require scrambling ability or rock climbing; while there are rock climbs directly up the flanks, the only other way of reaching the summit via a ridge is the south-west ridge, a Grade 3 scramble that begins up a scratched chimney which can be accessed from the summit of Sgùrr Sgumain or from Coir' a' Ghrunnda; there is also a slightly easier route from the top of this chimney directly up a shallow gully on the south face. The summit of Sgùrr Alasdair can be attained by a short detour (from Sgùrr Theàrlaich) off the main ridge by climbers undertaking the full traverse of the Cuillin ridge, or by those following the circuit of Coire Lagan.
The Great Stone Chute (with pale streak up it) leads up to Sgùrr Alasdair (which is in the cloud)