Essebsi, who served as a parliament speaker under Ben Ali, defeated incumbent interim President Moncef Marzouki in the presidential runoff on December 21.
Essebsi, the leader of the centrist Nidaa Tounes Party, won 55.68 percent of the votes.
The new president is due to start his official tenure on January 14.
But the return of a former Ben Ali old guard stalwarts like Essebsi has worried opponents.
"I am committed to be president of all Tunisian men and women without exclusion," the secular Essebsi said at the swearing in ceremony at the parliament. "There is no future without consensus among all parties and social movements."
The president's Nidaa Tounes party also holds the most seats in the new parliament. But Nidaa Tounes will be forced to negotiate a coalition government with smaller parties. It also faces tough rivals in Ennahda, who won the first election in 2011, and now hold the second largest number of seats in the parliament.