Devoted to martial arts, Tien is an honorable combatant and assassin. He trained under Master Shen, who was Master Roshi's rival and tried to kill Son Goku in the Martial Arts tournament. However, Master Shen showed incredible dishonor by trying to kill the child the night before the fight, making Tien stop being an assassin.
During his fight with Son Goku, Tien wins through sheer luck and instead of killing Son Goku, offers the child half his winnings and becomes friends with Son Goku and a friendly rival to Yamcha.
When King Piccolo is freed from his imprisonment, Tien decides to atone for his past deeds by sacrificing his life to use the Evil Containment Wave to stop him. Fortunately for him, Son Goku is able to kill King Piccolo, though King Piccolo spit out an egg containing his reincarnation.
Unlike Yamcha, who quit fighting after being outclassed by the Saiyans and Saiyan-Human Hybrids, Tien never stopped training and was even strong enough to delay Kid Buu from killing the more powerful heroes before he was killed.