Yuan Tan was born the eldest son of the powerful warlord, Yuan Shao. He accompanied his father to the famous Battle of Guandu against rival warlord Cao Cao in 200. Yuan Shao, however, was utterly defeated in the conflict and fell sick shortly after returning to his base city of . All along, Yuan Shao had intended to pass on his legacy to his youngest son Yuan Shang , who was said to be extremely handsome, but the successorship had not been clearly established by the time Yuan Shao died in 202.
Many officials intended to make Yuan Tan the successor according to seniority of the heirs but Shen Pei and Feng Ji , two influential advisors, supported Yuan Shang and pushed for him to inherit Yuan Shao's legacy. When Yuan Tan rushed back from his duty elsewhere, he could not revert the situation so instead he proclaimed himself General of Chariots and Cavalry , his father's former title.
In autumn of the same year, Cao Cao launched an offensive against the Yuan brothers. Yuan Tan stationed his troops in against the attack but his request for more troops was turned down by his brother, who feared Yuan Tan would take over military control. Yuan Shang then left Shen Pei to defend Ye and personally led a force to Liyang to assist in the defense. For half a year the battle went on but the Yuan brothers eventually gave up the city and retreated to Ye.
Cao Cao's advisor Guo Jia then suggested that the Yuan brothers would fight between themselves in the absence of an external enemy. Cao Cao took the counsel and withdrew his troops to attack Liu Biao in . Meanwhile, Yuan Tan and Yuan Shang indeed began to battle each other. After suffering initial defeats, Yuan Tan retreated to and sent out an emissary seeking to ally with Cao Cao. Cao Cao agreed and even married a daughter to Yuan Tan to strengthen the alliance.
Yuan Shang soon led a force to attack his brother again but had to retreat when he heard news of Cao Cao's siege on Ye. His force tried to converge with that in the city but the attempt was foiled. The defeated Yuan Shang then escaped north deep into the Wuhuan territory. Meanwhile, Yuan Tan violated the alliance by taking Ganling , Anping County , Bohai Commandery and Hejian into his realm. He also took over some former troops of Yuan Shang after the latter went into exile. Cao Cao then turned his force against Yuan Tan, who retreated to . In 205, Yuan Tan was eventually defeated and executed by Cao Cao.
Yuan Tan in Romance of the Three Kingdoms
''Romance of the Three Kingdoms'', a 14th century historical novel by Luo Guanzhong, was a romanticization of the events that occurred before and during the Three Kingdoms era. In Chapter 33, Yuan Tan was said to have sent Xin Ping as an emissary to Cao Cao while besieged in Nanpi County to seek surrender but was declined. When Xin Ping returned, Yuan Tan accused him of treason since his brother Xin Pi served in Cao Cao's camp. The undue accusation angered Xin Ping so much that he soon died, much to Yuan Tan's regret.
The next morning, Yuan Tan placed the commoners, who were hastily armed during the night, in front of his troops and marched into battle with Cao Cao outside the city. Yuan Tan was subsequently killed in battle by Cao Hong .