It starts to the west of Wellingborough town centre on the A5128 (formerly A45) and heads east, bypassing the town centre to the south. It crosses the A5193 (also formerly A45) at a set of traffic lights; this is the original western end of the B571 but it had been extended west to its current terminus by the mid-1920s.
The road crosses the B573 (which has priority) then goes over the River Ise and the Midland Main Line to enter open country. It then heads northeast and soon reaches Irthlingborough, where it meets the B5348 (formerly A6) at a roundabout at the far end of the High Street. The B571 is the dominant partner in a short multiplex east before the two roads separate by the B571's having to TOTSO left onto Addington Road. It ends a short distance further on on the A6 Irthlingborough bypass.