The cub's mother, Hao Hao, immediately took the hairless male, which entered the world at 2:02 a.m. (0002 GMT) on Thursday, in her jaws to protect it and clean it.
"Hao Hao's first son is right now in the best of health and weighs 171 grams (six ounces)," the zoo said in a joint statement with the China Conservation and Research Center for the Giant Panda.
"Less than 2,000 pandas can be found in the wild, making every birth a true miracle," the statement added, about 1,800 freely roaming and 400 in captivity, mainly in southwest China.
The cub has not yet been named, but officials have already started considering their options.
"The name will be beautiful and Chinese, but Belgians will be able to pronounce it," the veterinary team said in a statement.
China loaned Hao Hao and her mate, Xing Hui, to Belgium for 15 years in February 2014 to mark Chinese President Xi Jinping's state visit to the kingdom.
Hao Hao was artificially inseminated twice in February with the sperm of Xing Hui.
"It was very intense for us all. The utmost joy to see the birth," zoo director Eric Domb told RTL network. "It is also a big worry since the chances of survival of a panda are only one out of two in the first three months."
jbh/sms (AFP, AP, dpa)