Gavrilo Princip was born the fourth of nine children (six died in infancy). His father worked as a postman. Gavrilo, never in robust health, attended high school in Sarajevo and Tuzla, but in 1912 traveled to Belgrade for a more Serb-nationalist education. There he became an active propagandist for the Greater Serbian cause.

He was admitted to Major Tankosic's Black Hand partisan academy in 1912, but his poor health rendered him unfit for active duty. Two years later, Tankosic recruited Princip and two others for a plot to assassinate Archduke Franz Ferdinand. Because of his earlier partisan training, Princip was the best shot of the three and showed leadership qualities.

The assassination was ultimately successful. (See the Sarajevo article for a fuller account.) Police resuced Princip from the mob, many of whom wanted to kill him. Once in custody, Princip and Cabrinovic managed to confuse their amateurish interrogators, revealling nothing of the Black Hand organization and sponsorship of the plot. Danilo Ilic's confession nearly brought down their house of cards, but during the trial (in which all the defendants were present) Princip was quietly able to exercise his leadership. The code of silence held.

While some of the defendants expressed remorse over their crime, Princip maintained his silence about the Black Hand with a stoic detachment. His final statement in court was short.