In 1740 her father died unexpectedly at the age of 56, and Maria Theresa came into possession of the territories of Austria without having any political training. Her husband was an amiable man, but of mediocre mental endowments and consequently of little assistance to her. Charles, moreover, left the internal affairs of his monarchy, particularly the finances and the army, in a lamentable condition. His family regarded the future with misgiving and perplexity.

Maria Theresa was the first to recover her self-possession and to appreciate the problems before her. On the very day of her father's death, she received the homage of Privy Councilors and nobility as Queen of Hungary, Queen of Bohemia, and Archduchess of Austria, and at her first cabinet meeting expressed her determination to uphold to the full every right she had inherited. All admired her firmness, dignity and strength of spirit. Certainly they were few who believed she would succeed.

Theresa had to fight a few wars to maintain the borders of her empire. She gave a far reaching privileges to her army and nobles. For the promotion of trade and industry a bureau of commerce was established in 1746, but its development was hindered by the internal duties. The overseas trade greatly increased. The army was improved, the Prussian army being taken as a model; in 1752 a military academy, and in 1754 an academy of engineering science were established.

The empress also gave her attention to education and especially to the middle and higher schools. The gymnasia received a new curriculum in 1752. The medical faculty of the University of Vienna, after being long neglected, was raised to greater efficiency. The legal faculty also became a strong body. Moreover, the empress founded the academy of the nobles (Theresianum) and the academy for Oriental languages as well as the archives for the imperial family, court and state, which since 1749, had been a model of its kind. She did not permit any oppression of the working class either.

For the well-being of the state she decided on the separation of administration and justice. For the administration of the law, the Supreme Court was established. In 1753 the empress appointed a commission to compile a new Civil Code, which was published after the Napoleon's in 1811. During her reign (1768) the "Constitutio Criminalis Theresiana" was also promulgated for criminal law. Up to that time a heterogeneous procedure prevailed in the different countries.

Centralization was also aided by the creation of new district officials who were to carry out the measures of the government in the several countries. As they had often to protect the subjects against the oppression of the lords, the people became much more devoted to the government. Maria Theresa adopted the principle "cujus regio, ejus religio", and defended unity of faith in the State not only for Christian and religious, but also for political reasons

She was tireless in her care for the welfare and education of her children; she was the mother of sixteen, among them was Maria Antoinette, the future tragic French queen killed on guillotine. When they were at a distance she carried on a busy correspondence with them and gave them wise instruction and advice. Shortly before her death, being sick already, she made her will and in it directed, which was characteristic of her, besides generous bequests to the poor, the granting a month's pay to the soldiers. certain bequests on paper, among them, again, characteristic of her disposition, 100,000 florins for the funds of the normal schools. She died, at the age of sixty-three years in 1780.