Jason Grace was described as handsome and attractive: the regal features of a Roman statue, sky blue eyes, close-cropped blond hair that grew out during his time at Camp Half-Blood, and a small scar on the corner of his lip from trying to eat a stapler when he was two years old. Piper noted that his face was kind and gentle, but always looked a little sad.

He once observed that he looks nothing like his father, which assumes that he looks more like his mother. He is very tall, being one inch taller than Percy Jackson, despite being nearly a year younger, with an athletic build, and having well-muscled and tanned arms and legs. His tattoo has the picture of an eagle with SPQR and twelve lines, indicating he has been at Camp Jupiter since he was three or four years old. Piper noted that his eyes seemed to hold some deep sadness, much like her father's. After his encounter with Sciron, Jason's hair has had a groove in it where the Celestial Bronze bullet grazed it and was noted to have gotten taller.

His looks attract female attention, such as the instances with Drew Tanaka, and the girls from Wilderness School. Also, when Aphrodite gave Jason's team a makeover, Jason was the least modified, implying thatAphrodite approves of his physical attributes.

In The Blood of Olympus, Jason started wearing glasses made out of Imperial Gold due to being diagnosed byAsclepius as nearsighted.