A Syrian suicide bomber targeted the heart of the city's Sultanahmet district, popular with tourists and home to the Blue Mosque, in the January 12 attack which left 16 others injured.
Former prime minister Ahmet Davutoglu said at the time that the suicide bomber, named as Nabil Fadli, was a member of the Islamic State (IS) group.
The five men were released by an Istanbul court today because of the nature of their alleged offences, the available evidence and the length of time in custody, Dogan news agency reported.
The five men were named by the news agency as Mustafa Sraiwel, Muhannad Hendawi, Ibrahim El Ibrahim, Muhammed Izghib and Muhammet Isa. The nationalities were not given.
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The court imposed a travel ban on the five men while thirteen other suspects were ordered to remain in custody.
The defendants all denied the charges.
In total, Turkish authorities arrested 26 suspects in connection with the attack on a German tourist group.
The court heard from various defendants insisting they had no links to Islamic militants.
During the hearing, Hendawi said that Fadli told him he was studying to be a dental technician as he said that he had only met the attacker once in a restaurant, the news agency reported.
The trial was adjourned to September 5.
Turkey has suffered numerous attacks in the last 12 months blamed on IS extremists, including the triple suicide bombing on June 28 at the country's biggest airport.
47 people were killed and 200 injured after the gun and bomb attacks at Istanbul Ataturk airport. The country has also been hit by deadly attacks blamed on Kurdish militants.