The museum closed its doors in 2003, amid the chaos following the US-led invasion of Iraq, and was later ransacked by Islamic State after they seized the city in 2014.
"We are celebrating today, in the city of two springs, the launch of the Mosul Museum's rehabilitation project," the director of Iraq's antiquities authority, Laith Majid, said at a press conference.
"This museum, an icon of museums in Iraq, was targeted by a blind barbarian assault," Majid said, referring to the destruction by ISIS.
The militants used sledgehammers and power tools to deface ancient statues and pre-Islamic treasures housed in the museum, releasing an infamous video showing the destruction in 2015.
A gaping hole remains in the floor of the museum's famed Assyrian gallery, caused by a bomb explosion.
"Part of this cavity will be preserved, as a witness throughout history to what has been perpetrated," said Khair al-Din Ahmed Nasser, head of antiquities in Nineveh province, of which Mosul is the capital.
A new display was inaugurated, showcasing the museum's history, collection and current restoration plans, as part of efforts supported by France's Louvre Museum, the Smithsonian Institute and the World Monument Fund.
It comes within the "second and final phase" of the "total reconstruction and rehabilitation of the museum building" and should be completed within two or three years, said Nasser.
Among the pieces defaced by IS and under restoration at the museum are treasures from the ancient Assyrian site of Nimrud, including a winged lion, two imposing "lamassu" -- winged bulls with human heads -- and the throne base of the ninth century BC King Ashurnasirpal II.
"Out of five works, there are three that are extremely advanced," said Barbara Couturaud from the Louvre.
The artefacts are being revived with financing from the International Alliance for the Protection of Cultural Heritage in Conflict Areas (ALIPH).
"The pieces have been identified... now they have to be assembled. These are sculptures that weigh several tonnes, requiring extremely complicated handling," she said, adding she hoped they would be ready for the planned full reopening in summer 2026.