Gunmen kidnapped a British doctor working with the International Committee of the Red Cross (ICRC) in the southwestern Pakistan city of Quetta on Thursday, police and the ICRC said.
No one immediately claimed responsibility, but criminal gangs have often targeted foreign aid workers in the hope of securing large ransoms for their release.
"Health programme manager Khalil Rasjed Dale, a British national, was on his way home from work in a clearly marked ICRC vehicle when he was seized some 200 metres away from an ICRC residence," the ICRC said in a statement.
"The ICRC currently has no indication as to the abductors' identities or motives... Despite the incident, the ICRC will be continuing its humanitarian work in Pakistan."
Four health workers, including two doctors, were kidnapped by militants last week from the Pishin area of Baluchistan, near Quetta. They were freed after a shootout between police and their kidnappers.
The Geneva-headquartered ICRC also said it was scaling down its work in the country and closing six of its 10 offices.
The move was not due to Thursday's kidnapping, officials said, but due to "operational difficulties".
"The main reason we are scaling down is because of increasing difficulties in accessing certain areas and populations," said Narej Resich, ICRC communications delegate in Islamabad. "The main bulk of our health work will continue."
Resich refused to comment on whether the difficulties were related to Pakistani authorities denying aid workers access to areas or whether it is was due to fears over security of staff.
He said three offices in northwestern Khyber Pakhtunkhwa province were being shut down, as well as three in Lahore, Muzaffarabad and Jacobabad. Offices in Islamabad, Quetta, Karachi and Peshawar will continue to function.