Essebsi, 92, was taken to a military hospital after suffering what the presidency called a "severe health crisis". Essebsi had been briefly hospitalised last week as well.
Tunisian President Beji Caid Essebsi's health condition has begun to improve, a presidential adviser told Reuters on Thursday.
The 92-year-old was rushed to hospital in critical condition, a close aide said on Twitter.
Essebsi, 92, was taken to a military hospital after suffering what the presidential office called a "severe health crisis".
One of Essebsi's advisers told Reuters he was in a "very critical" condition but was alive.
The aide, Firas Guefrech, also said on Thursday that Essebsi's condition was "stable."
"Please do not be misled by rumours," Guefrech added.
Tunisian Prime Minister Youssef Chahed said on Facebook that he visited Essebsi in hospital and called for people to stop spreading "fake news" about his health.
"I assure Tunisians that the president of the republic is in the process of receiving all the necessary attention from the most efficient medical practitioners," he wrote.
The elderly head of state was also hospitalised last week for what the presidency described as non-serious treatment.
Tunisia’s first freely-elected president, Essebsi took office in 2014. He recently announced he wouldn’t run in elections this November, saying a younger person should lead the country.
The elections will be the third set of polls in which Tunisians can vote freely following the 2011 revolution that toppled autocrat Zine El Abidine Ben Ali, who ruled for 23 years.
Tunisia set itself on a path to democracy without much of the violence seen elsewhere, although it has been the target of Islamist terror groups over the years.
On Thursday, two suicide bombers blew themselves up in attacks on police in the capital Tunis, killing one officer and wounding several others. Terror attacks in 2015 left dozens of people dead, driving away foreign tourists and investors alike.
Read more: Tunis suicide bombs kill police officer, injure at least 8
Essebsi, a former parliamentary speaker under Ben Ali, has been the dominant figure in the North African country since his election in 2014, despite constitutional rules limiting his powers to defence and foreign relations. But he has lost influence since prime minister Youssef Chahed took office as prime minister in 2016.
His party has not yet identified another candidate for the upcoming election.