Estinien is a stoic character, often speaking in a brusque manner. He has little respect for those as he sees as weak, and does little to hide his disdain when speaking to them. He has spent the majority of his life being driven purely by his desire of vengeance against Nidhogg, and thus sees little need for companionship with others.

His personality softens somewhat, however, after spending time traveling with the Adventurer and their companions. Though his rude manner of speaking never changes, he eventually admits that it was through these friendships that he was able to move past revenge being his sole motivation. Though he often speaks insultingly to him, he forms a close bond with Alphinaud. Aymeric suggests that Estinien sees Alphinaud as a reflection of the younger sibling he lost to Nidhogg's flames, while Alphinaud sees Estinien as the older brother he wishes he had.