Sergeant Santos Cardona, 32, was convicted on Thursday of two out of nine counts against him - failing to handle his dog properly and using the unmuzzled Belgian shepherd to threaten one detainee, Kamel Mizal Nayil, with a force "likely to produce death or grievous bodily harm".
He faces up to three and a half years in prison.
Cardona was acquitted on charges of conspiring with a fellow guard to terrorise inmates into defecating and urinating on themselves.
The verdict comes as the US military investigates new allegations that marines killed two dozen Iraqi civilians in an unprovoked attack in November in the town of Haditha.
Despite evidence during the court-martial of pressure from Washington to extract more information from prisoners, there are few signs that senior Army leaders or administration officials will be charged with condoning the abuse.
Harvey Volzer, Cardona's civilian attorney, said the use of dogs to intimidate prisoners was condoned by officers and that Cardona was a victim of a confused chain of command.
Prosecutors characterised Cardona and other guards on the night shift at Abu Ghraib as rogue "corrupt cops" who tormented detainees for amusement from late 2003 to early 2004.
Another Abu Ghraib dog handler, Sergeant Michael Smith, was convicted in March and sentenced to 179 days in jail. No soldier above the rank of staff sergeant has been convicted of abuse at Abu Ghraib.
The US government, which often justifies its foreign policy on the ground of improving human rights, was severely embarrassed when photographs showing prisoners being abused and sexually humiliated were leaked in 2004.