Jihadist groups mounted a coordinated assault on security installations in the town on the border with Libya last March 7, aiming to win over residents and establish an "emirate" of the Islamic State jihadist group, according to Tunisia's authorities.
At least 55 assailants were killed, along with 13 members of the security forces and seven civilians.
Tunisia, which was the target of several IS attacks in 2015 in which 72 people were killed -- 59 of them foreign tourists -- has since been spared any major jihadist violence.
"March 7 is no longer an ordinary day in Tunisia. It has a symbolic value," the prime minister said at a ceremony held under tight security.
"To the inhabitants of Ben Guerdane, the town of resistance, your victory in the March 7 battle, the victory of security agents, of our soldiers, marked a turning point in the struggle against terrorism," Chahed said.
An analyst with the International Crisis Group, Michael Ayari, said residents and security forces in Ben Guerdane had shown "resilience, but that doesn't mean Tunisia is immune" to the jihadist threat.
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The attacks in 2015 and on Ben Guerdane in 2016 were followed by stronger security cooperation with Tunisia's Western allies, especially in military equipment and on supervision of the 500-kilometre (300-mile) border with Libya.
Defence Minister Farhat Horchani backed up Chahed's point.
"We showed that terrorism has no future in Tunisia... So long as the state is united, that the population is united, we will defeat this scourge," he told AFP.
During his visit, the premier announced several projects for Ben Guerdane, which is in southern Tunisia that has suffered neglect by central authorities.
The town of 60,000 inhabitants lives off trading, mostly smuggling goods across the border with chaos-strewn Libya.
"I have a message for our politicians: they haven't delivered on even one percent of their promises," said a brother of Abdelatti Abdelkarim, a victim of last year's attacks, echoing local distrust of the authorities.
"What we did (on March 7, 2016), that was to protect our country, our children, not for you," he said on Shams FM radio.