Wildlife rangers confirmed they found their butchered carcasses in a village in Garissa County.
A male white giraffe is still alive and is believed to be the only one of its kind left on the planet.
“This is a very sad day for Kenya,” said reserve manager Mohammed Ahmednoor.
“We are the only community in the world who are custodians of the white giraffes.”
“This is a long-term loss given genetics studies…has now gone to the drain,” added Mr Ahmednoor.
“Further to this, the white giraffe was a big boost to tourism in the area.”
Their appearance is due to a condition called leucism, which causes skin cells to have no pigmentation.
The poachers have not yet been identified and the motive for the killings remains unclear.
Experts from the Kenya Wildlife Society are now investigating the shocking slaughter.