Eren is hardheaded, obsessive, strong-willed, passionate, and impulsive. Physically, he's 19 years old, has a fairly long, yet rounded face, and sizable, expressive, teal-green eyes. His eyebrows are sparse and often furrowed, making him seem troubled or annoyed. Eren's hair is shoulder-length and dark brown, with his bangs falling naturally into a middle-parted, curtain-type style. His complexion also seems somewhat tan. After his training and during his time as a soldier, he became very physically fit and muscular.

He cares deeply for his friends and loved ones and will stop at nothing, even willing to mutilate himself and kill other people, just to ensure that they're safe and that they get to live long happy lives. Since witnessing his mother's gruesome demise and losing contact with his father, his fierce protectiveness to those he has left has only intensified. He can be extremely clingy and possessive over anyone he's romantically interested in.

Eren was injected with Titan serum of the founding Titan and the attack Titan which later causes him to be able to shift into Titan form. He cannot speak in his Titan form but he growls.