The monarchy initially ended in 1945 during the popular revolution in August. It was not abolished per se, rather the last Emperor of Vietnam abdicated in favor of new republican government.

After the revolution, the former Emperor returned as the Head of the State of Vietnam, a constitutional monarchy and client state of France. The state controlled most of Vietnam until the partition of Vietnam in 1954, after which he ruled south of the 17 parallel.

Finally, in 1955, the referendum held south of the 17 parallel ended the monarchy. A new republic was proclaimed, called the Republic of Vietnam. North of the parallel formed the Democratic Republic of Vietnam. As he was no longer the monarch, the last Emperor Bao Dai simply left the country in a self exile.

The fate of Bao Dai, compared to the last monarch of other countries like China and Korea was lenient. He was not imprisoned nor killes after he was ousted. But the monarchy of Vietnam had long ago diminished, and their fate overshadowed, that the last Emperor simply left. The officials and generals formally owing allegiance to him swore to the French, then to Ngo Dinh Diem, the President of South Vietnam who ousted him, and ultimately to themselves. The people no longer saw him and his regime as a worthy leader. And he was used, first by the French, then the Japanese, then the revolution leaders and the officials and generals. There was no reason to stay and all the reasons to leave.

The monarchy ended because it could no longer be the torch bearer of revolution and independence. It no longer had the reputation and authority to command. So when it ended, it did not leave impact as much as when South Vietnam ended. The good the last Emperor did, first abdicating and then continuing to call for independence of Vietnam as much as he could, however did earn him respect from some Vietnamese.