Penshaw Monument will be lit red, white and blue tonight following Saturday's terrorist attack in London.
Sunderland's Magistrates Court building in Keel Square will also be lit up as a mark of solidarity with people in the capital, while the Union flag is flying at half mast at Sunderland Civic Centre.
Councillor Paul Watson, leader of Sunderland City Council said: "This was a deeply shocking attack on innocent people enjoying a Saturday night out.
"Our thoughts and prayers are with all those affected by this appalling assault and with their families and friends.
"I know I speak on behalf of everyone in Sunderland in sending our sympathies to them.
"Once again we've seen a swift and reassuring response by the emergency services.
"We've also heard of inspiring acts of bravery on the part of the police and passers-by and tremendous kindness shown by ordinary people who came to the aid of those caught up in the attack.
"The people of London will not be bowed by this cowardly attack any more than the people of Manchester were two weeks ago.
"It's appropriate that we as a city show our solidarity with the people of London by lighting Penshaw Monument and the Magistrates Court building in Keel Square in the colours of the Union flag."
Sunderland will also be joining the rest of the country in observing the national minute's silence at 11am on Tuesday which is being held as a mark of respect to all those who died and were injured.
Penshaw Monument and the Magistrates Court building will remain lit in the colours of the Union flag until Thursday.