After crossing the river Aller at Rethem in Soltau-Fallingbostel district it passes through the villages of Groß Eilstorf and Kirchboitzen before entering the one-way system in the town centre of Walsrode.

The B 209 then passes through Honerdingen, before reaching junction 47 on the A 7 autobahn located in Bad Fallingbostel's industrial estate.

Near Artlenburg the B 209 crosses the Elbe Lateral Canal, the bridge being combined with a barrier.

Near Lauenburg the B 209 crosses the Elbe, passes over the B 5 and runs finally into Schwarzenbek, where it meets the B 207 and B 404.

To 1 July 1989 a section between Bad Fallingbostel and Soltau, part of the present day L 163 state road, was designated as Bundesstraße 209.