Police said the helicopter hit a construction crane on top of a high-rise building and burst into flames. Debris fell onto the street below.
Flames and a large plume of smoke could be seen rising from the wreckage. The pilot was killed, along with one person in the high rise.
The helicopter crashed just south of the River Thames near the Underground and mainline train station at Vauxhall, and near the British spy agency MI6. The Ministry of Defense said it was not a military helicopter and not a terrorist attack.
The cause of the crash remains under investigation.
The Associated Press contributed to this report.