The mall, once one of the Kenyan capital's most upmarket shopping centres, was devastated by an intense fire that broke out during the September 2013 attack by Al-Qaeda-linked Shebab gunmen that left at least 67 dead.
Since then, the bullet-scarred building has been empty.
But Westgate director Alex Trachtenberg, speaking at a prayer meeting on Tuesday, said tenants were returning and were expected to begin refitting stores ahead of a July opening.
"As the management and directors of Westgate Mall, alongside our esteemed tenants, we are today joined in this interdenominational thanksgiving and prayer service as we prepare for the reopening sometime in July," Trachtenberg said.
Atul Shah, who heads the key regional supermarket chain Nakumatt - whose store in the mall was where many of the victims were slaughtered - said they were readying to reopen.
"The fall of Westgate following the attack two years ago was a big blow to our business," Shah said. "I am however glad to confirm that our customers, among other partners, have enabled us to overcome the challenges."