The A1209 is a short A-road in east London which shadows the route of the A1208 slightly further to the north.
It starts at traffic lights on the A10 next to Shoreditch High Street station and begins by heading east alongside the station, which was built in a huge concrete box. The road bends to the left as the B135 continues ahead; this road has a prohibition for traffic on Sundays owing part of it being used for the Brick Lane Market. Brick Lane itself (the B134) is soon met at traffic lights, after which the road straightens.
The road continues east through the suburbs of Bethnal Green. It goes under the West Anglia Main Line to end at a signalised crossroads on the A107 opposite St John's Church, with the actual Green and Bethnal Green tube station adjacent.