The army, along with militias loyal to the government, seized the city and chased out ISIS fighters, al-Ikhbariya TV reported. The Russian air force was key in taking back Palmyra, according to Syria's state-run SANA news agency, quoting army command.
"This victory helps in further tightening the noose around ISIS terrorists," the army told the news agency.
ISIS militants seized control of Palmyra in May and immediately started demolishing ancient ruins considered among the world's most treasured
Last week, the army recaptured Palmyra Castle from ISIS
and destroyed hideouts, sending militants fleeing in various parts of the city.
Syria's army marched toward the city, dismantling explosives left behind by the terror group.
By Sunday, the army had seized the entire city, state media reported.
Months of destruction
The army's seizure comes after the Islamic extremist group went on a months-long rampage of destruction.
After it seized the city in May, it started destroying historical sites
a month later, expanding its conquests and showing its contempt for the people and their history.
Syria said ISIS destroyed two Muslim holy sites: a 500-year-old shrine and a tomb where a descendant of the Prophet Mohammed's cousin was reportedly buried.
Antiquities expert beheaded
Two months later, the terror group destroyed more antiquities, including the 1,800-year-old Arch of Triumph
and the nearly 2,000-year-old Temple of Baalshamin
. ISIS also beheaded the antiquities expert who looked after the ruins.
UNESCO, the U.N. agency that documents the world's most important cultural and natural sites, called the temple's destruction a war crime.
Palmyra, in the Homs countryside northeast of Damascus, was a caravan oasis with various influences.
Its art and architecture are a mix of Greek, Roman and Persian influences, according to UNESCO
ISIS has been unapologetic about its devastation of the ancient city, even publishing photos detailing the destruction
Irina Bokova of UNESCO said the world body plans to review the damage.
"For one year, Palmyra has been a symbol of the cultural cleansing plaguing the Middle East," Bokova said.
"As soon as security conditions allow, UNESCO is ready to go to Palmyra with those responsible for Syrian antiquities on a mission to evaluate damage."
Bokova said those responsible for the destruction will be punished.
ISIS claims it's in control
After news that Syrian troops were poised to retake Palmyra last week, ISIS released a video claiming it controls the city.
It shows the city's deserted streets and cuts to an ISIS militant sitting on a tank, saying the group will defeat any forces that enter the city. The video shows a panoramic shot of Palmyra's ruined historical site.
CNN cannot independently verify the authenticity of the video.