The Highways Agency is resurfacing the road in both directions and renewing markings between Junction 3 of the M25 near Swanley and the A224 at Crittalls Corner near Sidcup.
The work, which is part of record roads investment, will improve road safety and ensure smoother journeys for road users.
It will take place between Tuesday 22 April and Tuesday 6 May on the eastbound carriageway and between Wednesday 7 May and Saturday 31 May on the westbound carriageway. The road will be closed in one direction at a time with local diversion routes put in place.
Tommy Whittingham, Asset Manager for the Highways Agency, said:
This work is part of our commitment to safe and reliable journeys on the A20, providing an improved experience for road users between London and Kent.
Work will take place overnight – and avoid weekends - to minimise disruption to road users and local residents.
Additionally we will monitor noise levels during the night to ensure there is minimal disturbance.
The work will take place overnight between the hours of 10pm and 5.30am, Mondays to Thursdays, and between 11pm and 6am on Fridays.
While the eastbound carriageway is closed, a diversion route will take road users via Crittalls Corner onto the A223 Edgington Way, then via the Ruxley Roundabout onto the B2173. Road users can then rejoin the A20 at the M25 Junction 3 roundabout.
While the westbound carriageway is closed, a diversion route will take road users from the M25 Junction 3 roundabout onto the B2173 westbound, where they can rejoin the A20 at the B2173 Maidstone Road.
Members of the public should contact the Highways Agency Information Line on 0300 123 5000
Journalists should contact the Highways Agency press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer