Military personnel fired gunshots after a driver attempted to ram the gates.
A man was then detained with cuts and bruises and taken into custody.
Suffolk Police earlier said officers were responding to reports of a "significant incident at RAF Mildenhall".
Flights in and out of the base were temporarily suspended.
Senior Master Sergeant Brian Boisvert said: "We are working right now in partnership with Suffolk Police to make sure we have a good working relationship, to make sure this incident is taken into account, and that everyone remains safe.
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"Things are not back to normal prior to what happened but we are no longer in lockdown."
"At approximately 14:35 we were released from lockdown and an all clear was given and then we went into recovery emergency operations."
It is currently not being treated as a terror incident and no other injuries were reported.
The BBC’s Home Affairs Correspondent Daniel Sanford earlier tweeted: “The early indications are that someone tried to drive onto the base and was stopped at the gate, and has been arrested.
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“People nearby heard gunshots.”
American children at a nearby play area in the village “suddenly left” after the incident.
A staff member at Jumppin Jacks Funhouse said: “All the American children playing here suddenly left, but we didn’t hear anything or know why.”
The incident is now under control and the base is no longer on lockdown, a spokesman for the base confirmed.
A brief statement on the base's Facebook page said: "RAF Mildenhall locked down at 1pm today following reports of a disturbance on base.
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"The base was locked down and emergency personnel are responding to the situation.
"Additional details will be provided as they become available."
Last year Junead Khan was convicted for planning a terror attack on US military personnel having apparently scouted out RAF Mildenhall as a target.
The delivery driver drove close to several bases operated by the US, his trial was told.