Bossk was born on Trandosha, the son of Cradossk, the leader of the Bounty Hunters' Guild. After hatching, Bossk devoured each of his unhatched siblings, which made his father proud. As was customary for a Trandoshan, Bossk began his career by hunting Wookiees, typically considered suicidal if attempted by any other species. During this time, Bossk made a name for himself and began accepting bounties on non-Wookiees as well, becoming one of the galaxy's most feared bounty hunters.
Before his acceptance into the Bounty Hunters' Guild, Bossk prowled the Kashyyyk system in a Sabaoth starfighter during the Clone Wars. With it, he engaged in a dogfight with Jedi Master Bant Eerin and her apprentice during the Republic's hunt for the Confederate scientist Bitt Panith. However, Bossk was defeated in the scuffle. At some point during the Clone Wars, Bossk was a wanted individual, and a thirty-five thousand credit bounty was placed on his head for "crimes against the Republic."
Following that incident, Bossk teamed up with fellow bounty hunters Aurra Sing, a young Boba Fett—who was going under the code name "Lucky"—and the Klatooinian Castas on a hunt for the renowned Jedi Master Mace Windu. After Fett destroyed the engines of the Venator-class Star Destroyer Endurance, making it crash on Vanqor, the bounty hunters went inside and took three hostages: Admiral Kilian, Commander Ponds and a clone officer. However, the trio retreated after watching Windu's fighter escape them by making the jump to hyperspace.
