The incident has sparked congestion to Limehouse back along the Highway and back to Aldgate.
A hooded person was spotted climbing the landmark bridge and sitting on the suspension railings.
Emergency services were called to the bridge shortly before 11am today (March 10).
City of London police has urged people on X to avoid the area as the incident is being dealt with.
The bridge has been closed in both directions, leading to congestion between Limehouse and Aldgate as buses are on diverted routes through the city.
Meanwhile, the Blackwall Tunnel is also shut southbound following a crash.
Police have confirmed a lorry crash with part of the tunnel at around 8.50am.
The full City of London Police says: “Tower Bridge is closed to traffic and pedestrians due to a person who has scaled the railings.
“Please avoid the area where possible.”
