Nicholas Joestar was a scrawny young man who had a regular haircut featuring spiked interlaced locks of hair at the top of his head, appearing similar to a crest.
In the past, Nicholas is shown as kind and sympathetic to his much younger brother Johnny. He seems to be a good student too as his teachers trust him and would lend him a mouse corpse to fool his father about Danny's death.
Nicholas is capable of controlling large horses like his own perfectly, no different than when he is riding any other horse.
Nicholas is never a fraction of a second late. Whether Johnny tells him to run 200 meters in 17 seconds, or the next 200 meters in 23 seconds, he'll always finish exactly in that time. He was born with this ability, unlike his father.
When young Johnny once took his pet mouse Danny to secretly feed it under the table during dinner, his father, upon discovering it, ordered the child to drown the animal himself as punishment. Heartbroken, Johnny was unable to bring himself to do the deed, and followed Nicholas' suggestion to set Danny free into the woods instead.
At the time, Nicholas was a promising jockey-to-be, having already won several trophies which were put on his desk. One day while practicing for his next race, with a new horse named Black Rose, said horse stumbled from something on the ground, which cost Nicholas his life. Diego claimed a white mouse was the cause of the accident – a mouse who Johnny believed to be Danny. Seven years later, it was Johnny who rose to fame as a racing prodigy. However, his father still did not acknowledge him and his feats, even asking God "why He had taken Nicholas and not Johnny".
During the fight with Axl RO, Nicholas and Danny were seen once more, manifested from Johnny's guilt over freeing Danny and accidentally leading to Nicholas' death.