The bridge, the world's first single span made of iron, was erected over the River Severn in 1779.
Historians say the site is an important part of the early years of the Industrial Revolution.
English Heritage said the site has been damaged by stresses in the original ironwork and a 19th Century earthquake.
The work is set to begin in 2017.
Engineers have been investigating the bridge for the last three years, and are set to finish their examinations this week.
Kate Mavor, English Heritage's chief executive, said the renovations will ensure the Iron Bridge Gorge site "will continue to inspire us for generations to come".
"An iconic symbol of the Industrial Revolution, it is arguably the most important bridge ever built and without doubt, one of the most important sites in our care," she said.
The historic Ironbridge in Shropshire will receive £1.25m for essential maintenance work, it has been announced.