The verdict handed down to retired geologist Jim Fitton shocked the court in Baghdad, including his defence lawyer.
He and his family have argued that Mr Fitton, 66, had no criminal intent when he picked up 12 pebbles and some shards of broken pottery.
A German national tried with Mr Fitton was found not to have had criminal intent in the case and will be released.
Mr Fitton’s sister, Ruth Zacarello, 68, from Kirkcaldy, Fife, and her MP, Neale Hanvey, had campaigned on his behalf.
And an online petition calling for the case against him to be scrapped had garnered 300,000 signatories.
Mr Hanvey had previously criticised the Foreign and Commonwealth Office for backing claims that the former oil and gas industry expert had no case to answer.
Defence lawyer Thair Soud said: “I thought the worst-case scenario would be one year, with suspension.”
Judge Jabir Abd Jabir found that, according to the government’s investigation, Mr Fitton had criminal intent to smuggle the artefacts that he had picked up and intended to transport them out of the country.
The two men first appeared in court on May 15 wearing yellow detainees’ uniforms, telling judges they had not acted with criminal intent and had no idea they might have broken local laws.
Mr Fitton said he “suspected” the items he collected were ancient fragments, but that “at the time I didn’t know about Iraqi laws”, or that taking the shards was not permitted.
As a geologist he was in the habit of collecting such fragments as a hobby and had no intention to sell them.
In his defence, Mr Soud said Mr Fitton waited for weeks while in custody before hiring him as his legal counsel, arguing that this makes the point that the Briton had no idea of the severity of the case or the value of the goods found in his possession.
Mr Fitton and the German national, Volker Waldman, were arrested in Baghdad airport on March 20 after airport security discovered the items in their luggage.
They had been part of a tourism expedition across the country’s ancient sites.
Mr Fitton’s family grew worried when he did not arrive on a scheduled flight back to Kuala Lumpur, where he lives with his wife, on March 20.
The British diplomatic mission in Baghdad has not commented on its involvement in the case and the British consul in Iraq, who attended the court session on Monday, left following the sentencing without making any comments.
In total, 12 fragments of pottery and other shards were found in his possession by Iraqi authorities, all of them collected as souvenirs during a group tourism expedition to Eridu, an ancient Mesopotamian site in what is now Dhi Qar province.
The site is said to be among the oldest belonging to that civilisation.
A report by the Iraqi Culture Ministry stated the shards were over 200 years old, without offering any further explanation about their provenance. But any item less than 1,500 years old disqualifies it from being from antiquity, a period from the beginnings of Western civilization to about 450 AD.
Mr Fitton’s lawyer said he intends to appeal.