Lambeth Bridge and Vauxhall Bridge are among seven London river crossings listed by the culture secretary Andy Burnham.
Mr Burnham was joined by English Heritage chief executive Simon Thurley to make the announcement at Lambeth Bridge on Wednesday morning.
Lambeth has been listed at grade II and Vauxhall has been given grade II* status. The Department for Culture, Media & Sport says that the purpose of listing a building is to ensure that greater care will be taken about decisions affecting its future.
"London's bridges are the vertebrae of this great city's spine – the River Thames," says English Heritage chief executive Simon Thurley.
"Considering their architectural and historic contribution to the capital, a surprising number of these magnificent river crossings do not have statutory protection.
"I am therefore delighted that the minister has agreed with our advice and has awarded these spans listed status or upgraded their original listing. It is a fantastic endorsement of London's heritage."
The present Lambeth Bridge was built by the same firm which built the Tyne Bridge and the Sydney Harbour Bridge and opened in 1929 by King George V and Queen Mary.
The current Vauxhall Bridge was completed in 1906 to a design by Sir Alexander Binnie. It was the first bridge to carry trams across the Thames.