State news agency Beltra reported that Wednesday's ceremony is taking place in Minsk's capital with several hundred top government officials.
It comes after six weeks of mass protests against the official results of the Aug. 9 presidential election that resulted in Lukashenko's reelection after 26 years in office in office. The opposition in Belarus has challenged the election as rigged.
According to the official results, Lukashenko, who has run the ex-Soviet nation of 9.5 million with an iron fist, won 80% of the vote. The United States and the European Union have also criticized the violent police crackdown on post-election protests in Belarus.
During the inauguration ceremony, Lukashenko swore to "serve the people of the Republic of Belarus, respect and protect rights and freedoms of people and citizens."
After being sworn in, he was handed an ID card of the President of Belarus by the country's central election commission's head.