From 1923 to 1928 he was President of the National Council of Austria. On 10 December 1928 he was elected the President of Austria, a role he served in until the position ceased to exist ten years later when Austria was annexed by Germany in the Anschluss. In 1930 Miklas appeared on a set of Austrian postage stamps. In 1936 he entertained Miklós Horthy at Lake Wörth.

Miklas originally offered amnesty to jailed Nazi members, but refused to turn over the national police force to Arthur Seyss - Inquart, although after Adolf Hitler ordered military operations along the border, Miklas was forced to concede to their demands and installed Seyss - Inquart as the Austrian Minister of the Interior. Miklas was highly unpopular among Austrian Nazis because he refused to commute the death sentences imposed on assassins of Chancellor Engelbert Dollfuss after the failed putsch in 1934.

On 11 March 1938 Hermann Göring demanded that Seyss - Inquart replace Kurt Schuschnigg as the Federal Chancellor of Austria; otherwise, German forces would overrun Austria the following day. Miklas refused, and after Hitler received confirmation from Benito Mussolini that he would not interfere, it was announced that German troops would invade at dawn the following day. Miklas capitulated at midnight, announcing that he had instated Seyss - Inquart as the new Chancellor, but it was too late. When German troops rolled over the border at dawn the next day, they were largely greeted as heroes.

Miklas was disliked by many members of the Austrian Nazi Party at this point for his initial refusal to appoint them custodians of Austria, and it ended up being future Waffen - SS colonel Otto Skorzeny who protected Miklas during the Anschluss. He was placed under house arrest and abandoned the political sphere.

Miklas died on 20 March 1956 in Vienna.