One driver told Sky News that they saw a "large man was walking down the middle of the fast lane in a white vest covered in blood".
Motorists were warned to seek alternative routes while officers dealt with the man on the road near Maidstone.
A Kent Police spokesperson said: "Kent Police was called following concern for a man seen between Junctions 7 and 8 of the M20 near Maidstone at 11.45am on Sunday 17 March 2024.
“Emergency services attended and the man was located with injuries which are not believed to be life-threatening. He has been passed into the care of healthcare professionals.
"The motorway was closed in both directions while the incident was responded to and reopened by 1.30pm."
It comes as a five-mile stretch of the M25 between junctions 10 and 11 was closed in both directions at 9pm on Friday and remains inaccessible until 6am on Monday while a bridge is demolished and a new gantry installed in its place.
Concerns had been raised thousands of drivers would be stuck in gridlocked traffic over the weekend during the unprecedented closure on the south-west of the orbital route, with one councillor calling it a “nightmare”.
Congestion stretched for two miles on Saturday morning, according to National Highways South-East (NHSE), and the estimated average journey time through the diversion route was 25 minutes.
