His ancestors originated in the state of Qi 齊, and his grandfather Meng Ao 蒙驁 took part in the campaigns against the states of Han 韓, Zhao 趙 and Wei 魏. His father Meng Wu 蒙武 commanded, together with Wang Jian 王翦, the troops conquering the state of Chu 楚. Meng Tian himself had the post of a jurisdictional supervisor but he was made chamberlain for the capital (neishi 内史) in 221 after the state of Qi was conquered by Qin.
After the unification of the empire the only trouble for the territores of China were the intrusions by the peoples from the northern steppe federation of the Xiongnu 匈奴. Meng Tian was dispatched with a force of 300,000 troops to pacify the Xiongnu. He was able to secure the region north of the great Ordos bend of the Yellow River and had established 44 garrisons (shu 戍). Together with his brother Meng Yi 蒙毅 he took over the supervision of the Great Wall 長城 project, as well as the logistics network to supply the northern garrisons.
The permanent presence of a strong force at the northern borders was in fact able to repel the Xiongnu that would only start again harassing Chinese territory in the early weak decades of the Han dynasty 漢 (206 BCE-220 CE).
Although Meng Tian begged Fusu not to follow the order issued by the new emperor, Huhai 胡亥 (i.e. the Second Emperor 秦二世皇, r. 209-207), Fusu obeyed the paternal command and killed himself. Meng Tian and his brother were encarcerated. Huhai protested, but the mighty eunuch was stronger, had the brothers Meng sentenced to death and forced them to poison themselves.