A Pentagon spokesman on Friday said a third guard was acquitted of criminal charges after using pepper spray on a prisoner.
A fourth guard was given counselling after admitting to kicking the bed of a prisoner in hospital at Guantanamo Bay.
Allegations of misconduct by two other guards were not substantiated, the spokesman Air Force Major Michael Shavers said.
Around 600 non-US citizens are being held at Guantanamo in what President George Bush calls the global war on terrorism.
Human rights groups long have criticised the conditions under which prisoners are held at Guantanamo.
An army reserve specialist was charged with dereliction of duty and assault on a detainee following an incident in April 2003, Shavers said. The guard was accused of hitting a prisoner who already had been subdued.
In non-criminal punishment, the guard was reduced in rank to private, given 45 days of extra duty and reassigned to other duties.
Another army reserve specialist was charged with assault in September 2002 in an incident in which the guard sought to spray a prisoner with a hose after the prisoner threw what was believed to be toilet water at the guard.
Coming in the wake of shocking disclosures about prisoner abuses by US soldiers in Iraqi jails, US defence officials said the punitive actions taken against errant soldiers showed a very good system was in place at Guantanamo.