After the Hundred Year War and the tensions of the Harmony Restoration Movement conflict, Aang managed to maintain a period of peace. Together with his friend and the new Fire Lord, Zuko, he built the United Republic territory, where a metropolis named Republic City became home to people from all nations. Aang also found an island filled with lost flying bison, along with a new type of winged lemur, the ring-tailed winged lemur.

Some time during this period, Aang married Katara and the two had three children, named Kya, Bumi, and Tenzin. Tenzin, the youngest, was the only airbender; he was born when Aang was thirty-two years old. At some point, Aang built Air Temple Islands, where his son Tenzin would later reside.

In 128 ASC, Aang traveled to Republic City to help Toph arrest a criminal known as Yakone. After attending his arrest, Aang watched the trial, where Yakone was convicted of bloodbending. Yakone then used his bloodbending against the entire meeting room, leaving everyone unconscious. The Avatar State awoke Aang; allowing him to pursue the criminal. After stopping his escape, Yakone began bloodbending him again, this time intending to kill him. However, the Avatar State allowed Aang to break free of Yakone's grip. Aang captured Yakone in an earth shell before using energybending to remove his bending.

When he felt that his life energy was draining, he tasked the Order of the White Lotus to search for and watch over the next Avatar. Eventually, at the age of sixty-six, Aang passed away. His hundred years of being frozen in a state of suspended animation in the Avatar State eventually weighed heavily on his body, and drained much of his life energy during that time. The Avatar Spirit was then reincarnated into the Southern Water Tribe as a girl named Korra.