The strike on the convoy occured in an area that has experienced a wave of attacks by Taliban fighters.
The governor's convoy was the target of another bomb blast just two weeks ago.
The explosion struck one of the vehicles outside the city, wounding three policemen.
The outskirts of Kandahar city was also the site of the worst suicide attack in Aghanistan's history when a suicide bomber killed at least 100 people at a dog-fighting contest about a week ago.
By contrast, in the country's east, particularly along the border with Pakistan, attacks have decreased in recent months, according to a US general.
Brigadier General Joseph Votel, deputy commander of the US-led force working with Nato-led troops, said that the fall was due to "aggressive operations" by Afghan security forces and their Western allies, as well as improvements in local governance.
Votel said that the number of attacks in February was approximately 35 per cent below that for the same month last year.
He said: "Our border attacks and incidents along the border ... continues to go downwards. We are probably 40 to 50 per cent below what we were a year ago.
"We attribute this to aggressive operations there that we have been conducting with the police, with the army, assisted by the coalition forces ... and the growth of the government in the districts and in the provinces."
Votel played down the possibility of a Taliban-mounted "spring offensive".