"President Beji Caid Essebsi decided on Wednesday to extend the state of emergency for four months starting from Thursday, June 15," his office said on Facebook.
The state of emergency has been in place since a November 2015 jihadist bombing in Tunis that killed 12 presidential guards.
The Islamic State group claimed the attack as well as bombings earlier in 2015 at the Bardo National Museum in Tunis and at a beach resort near Sousse that killed a total of 59 foreign tourists and a Tunisian guard.
They were part of a wave of jihadist violence since a revolution toppled long-time dictator Zine El Abidine Ben Ali in 2011.
Signup to our newsletter and follow us on Facebook and Twitter!
The government has repeatedly renewed the state of emergency despite its assurances that security has improved in the North African state.
A source in the president's office, who asked not to be identified, said that after recent attacks claimed by IS in London and Manchester, "it's better to be vigilant".
The state of emergency gives much greater powers to the police and allows the banning of strikes and meetings likely to provoke "disorder", as well as measures "to ensure control of the press".
It also allows the interior ministry to place under house arrest anyone whose activities it deems a "danger for security or public order".
In recent weeks, the government has used the powers not just for counter-terrorism but also for a widely publicised "war on graft".
Ten businessmen are currently under house arrest on suspicion of corruption.