Sergeant Michael J Smith, 24, was found guilty of six of 13 counts. A judge later dismissed one of the counts, saying it duplicated another charge.
Smith faces up to eight and a half years in prison on the five remaining counts, forfeiture of all pay and allowances and a dishonourable discharge.
He had faced the stiffest potential sentence of any soldier charged so far in the Abu Ghraib scandal - up to twenty four and a half years in prison if convicted on all counts.
The military jury deliberated for about 18 hours over three days before announcing its verdict.
The government contended that Smith, of the 523rd Military Police Detachment, Fort Riley, Kansas, used his black Belgian shepherd to intimidate five prisoners for fun and competed with another canine handler trying to make detainees soil themselves.
In closing arguments on Friday, a prosecutor said Smith had violated two tenets of his training: Treat prisoners humanely and use the minimum amount of force needed to ensure compliance.
The defence argued that Smith was a good soldier who had done what he was supposed to do by having his dog bark at prisoners in a dangerous, chaotic environment where policies were so fuzzy that even the general who supervised interrogations testified he felt confused.
Smith was found guilty under the Uniform Code of Military Justice of two counts of maltreatment involving three detainees, one count of conspiring to make a contest of making detainees soil themselves, dereliction of duty, assault and an indecent act.
The soldier, wearing his green dress uniform, stood at attention staring straight ahead as a panel member read the verdict.