Carnedd Llewelyn lies in the middle of the main north-east to south-west ridge of the Carneddau, between Carnedd Dafydd to the south-west and Foel Grach to the north. A short subsidiary ridge links it to Yr Elen to the north-west. It can be climbed from Gerlan, above Bethesda, taking the path following Afon Llafar then continuing to the summit of Yr Elen before following the short ridge to Carnedd Llewelyn. Another path starts from Helyg on the A5, taking the track to the reservoir then following the slopes above Craig yr Ysfa to the summit. An alternative is to reach it by following the main ridge, either from Pen yr Ole Wen or from Foel-fras.