The five people were taken on Thursday night from a house they were sharing "allegedly for questioning" said MSF spokesperson Michael Goldfarb.
However, they have not been heard from since sparking suggestions they may have been kidnapped.
Information from Doctors Without Borders (MSF) has been sparse with officials declining to go into details about the missing personnel.
"We can confirm that our personnel who have disappeared are expatriates of Belgian, Danish, Peruvian, Swedish and Swiss nationalities," an MSF spokeswoman said in a brief statement to the AFP news agency.
The spokesperson defended their decision not to release any further information, such as the gender of the personnel, saying that "discretion is crucial for the security of our colleagues."
Belgian Foreign Minister Didier Reynders however told broadcaster RTL-TV that the Belgian national was a nurse in his 30s.
He emphasised though that it had not yet been established that the five had been kidnapped.
"We do not have confirmation from other sources (besides MSF), so I want to make clear that I'm talking only about a possible kidnapping," he said.
Several international media outlets have speculated that al-Qaeda sympathisers may be behind the latest incident in Syria.
In October, seven employees of the International Committee of the Red Cross were kidnapped in north-western Idlib province, with a Syrian NGO blaming the abduction on the Al-Qaeda-linked Islamic State of Iraq and the Levant.
MSF has six hospitals and four health centres in northern Syria and
provides health support from neighbouring countries to within Syria as well as to Syrian refugees.
A spokesperson for MSF Sweden said the humanitarian work in the region would continue and declined to add what measures have been taken following the disappearance of five staffers.
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"There isn't anything we can say about the current situation. The operation continues but the precautionary measures we take we have to keep to ourselves for security reasons," Karin Ekholm told the TT news agency.
She added that MSF's work in the region was vital as the existing health care system was "more or less destroyed."
In November two Swedish journalists were kidnapped in Syria. Reporter Magnus Falkehed and photographer Niclas Hammarström were leaving the village of Maaloula when they went missing and have yet to be released.