Twickenham and Teddington

The A309 starts in Strawberry Hill near Twickenham at a roundabout with the A310. It is named Waldegrave Road before meeting with the A313 at Teddington High Street. It then runs on a short stretch named Park Road. The first section of the A309 ends at the B358 north of Bushy Park, where Park Road continues towards the east and becomes Sandy Lane, and the westbound road is Queen's Road. Reaching the second part of the A309 is reached by travelling through Bushy Park (Chestnut Avenue) although since 2020 that has not been permitted by car.

Hampton Court to Hook

The second section of the A309 starts at a roundabout by Hampton Court Palace with the A308 in the Borough of Richmond upon Thames, Greater London, as a primary A-road. Heading into East Molesey, it passes the main entrance to the palace before going over Hampton Court Bridge. As it goes over the bridge, it enters the borough of Elmbridge, Surrey and becomes Hampton Court Way. It passes junctions with the A3050 and the B369 before the speed limit increases to 40 mph (64 km/h). In Thames Ditton, it passes a roundabout with the B364 (Embercourt Road), before heading near to Esher railway station.

It then enters Hinchley Wood and passes through the Scilly Isles Roundabout with the A307. The road then changes name to Kingston By-pass as a dual-carriageway. It passes near Hinchley Wood railway station just before a crossroads with Manor Road North and South. It then comes to a roundabout with Claygate Lane and the speed limit increases again to 50 mph (80 km/h). It heads through the edge of Long Ditton with a slip road heading to the A3. The A309 then continues for a short stretch before entering the Royal Borough of Kingston Upon Thames immediately before its eastern terminus at Hook Junction with the A243 and the A3.