The Taliban claimed responsibility for the attack. In a text message to reporters, Taliban spokesman Qari Yousef said the suicide bomber killed the deputy governor as well as three of his body guards and his driver.
The U.S. ambassador to Afghanistan, Karl Eikenberry, condemned the killing and offered his condolences to the official's family.
Kandahar, located in the Taliban's traditional southern stronghold, has been the scene of several attacks recently. Two weeks ago a bicycle bomb targeting police vehicles near the city center wounded at least 10 people -- six civilians and four police.
Last month, a suicide car bombing in the city center killed three people and wounded 26 others, most of them police.