Suffolk Constabulary said the 26-year-old was arrested on Wednesday and is being questioned over “information provided to the investigation”.
Mr McKeague, 23, from Fife, vanished on a night out with friends on September 24 in Bury St Edmunds, Suffolk.
Police said the arrested man is not the driver of a bin lorry which collected refuse from the area where Mr McKeague was last seen, but no further information was given.
The last CCTV sighting of Mr McKeague showed him walking from a shop doorway and into a horseshoe-shaped area in Brentgovel Street, with no sign of him emerging.
CCTV shows a waste lorry made a collection in the area shortly after the last confirmed sighting and the vehicle’s route appeared to coincide with the movements of Mr McKeague’s phone, but police said its load weighed less than 33lb (15kg) and forensic examinations found no trace of him in the lorry.
However, preparations are being made to search a landfill site in Milton in the next week.
Work has started to move some bulk material and build access routes to allow the search to get under way.
Detective Superintendent Katie Elliott said: “We are continuing to make progress on the investigation and we will be starting the landfill site search as soon as the preparatory work is complete.
“We have been carrying out a lot of inquiries behind the scenes and our work continues to find the truth about what happened to Corrie.”
Suffolk police still want to trace two potential witnesses who were in the Brentgovel Street area between 3.20am and 5.20am on Saturday September 24.