The incident occurred at a project at Mannhagen, Schleswig-Holstein, when the blade fell on to the crane cabin during installation.
Vestas said it was unclear what had caused the blade to fall and has commissioned a third party to conduct an investigation into the cause. The crane was operated by a subcontractor to Vestas.
This is not the first time a blade has fallen on a worker while installing a Vestas turbine. In April this year, a man was reported to have suffered chest and pelvic injuries at the MacArthur wind farm in Australia. Police were reported as saying he had been "caught by the turbine blade". Vestas denied the worker had been injured by a turbine component.
Fatal accidents are relatively rare during turbine installation and have been reduced proportionately in recent years. However, many of these have occurred in cranes.
In China last year, five people, including a Communist Party official, were killed after a crawler crane toppled while a contractor was rehearsing the installation of a Sinovel 5MW turbine.
The incident occured when the arm of the 1,000-tonne crane toppled and fell down suddenly during a trial operation to lift a wind turbine.
Other recent fatal incidents include a crash involving a 130-tonne crane near the 65MW Scout Moor wind farm in Lancashire, northern England in the UK, and an incident at the Agua Doce wind farm in southern Brazil, although exact details are unknown.