The extra money will be a major boost to the £3.3m TfL has already contributed to the project and will enable work to start sooner than planned, with a view to completion by the end of 2011, well in time for the 2012 Olympic and Paralympic Games.
"The visual and accessibility improvements planned for Exhibition Road will create an exciting and welcoming environment for all visitors," said head of NMSI events Victoria Grossmith, speaking on behalf of the Science Museum.
"Guests will benefit from a sense of destination and occasion when they arrive in South Kensington, making the Science Museum even more desirable as an event venue. I am really looking forward to seeing the results."
Work around South Kensington tube station has already started.