The paper identified the man as John Willis Downs from Arabic language court using a phonetic spelling of his name.
The paper did not say how long he had been in Qatar or where he was from in the United States.
The newspaper did not identify the embassy.
Secret gas project
The paper said the American was arrested on August 26, 2005, in a sting operation set up by Qatari police after arranging to collect an envelope containing $1,000 near a lamp post in Doha.
After the arrest, police searched the American's home and found a compact disc containing data collected over time, according to testimony.
"The information being sold would have endangered Qatar's economic security"
Abdullah al-Attiyah, Qatar's minister of energy
The man's co-workers at Qatar Petroleum told the court that he gained access to their passwords to collect information about the secret gas project.
The man's lawyer argued that his client was not selling government secrets and that the American had been entrapped by authorities who lured him to commit a crime.
Mirembe Nantongo, a spokeswoman for the US Embassy in Qatar, said on Tuesday that American authorities were aware of the sentencing but were prohibited by US privacy laws from commenting.
Downs remained in a Qatari prison pending appeal of his conviction.
Abdullah al-Attiyah, Qatar's minister of energy, testified during the trial that "the information being sold would have endangered Qatar's economic security and cost the country several billion riyals".
The paper did not provide information about the nature of the secret information.
However, Qatar is home to a number of high-technology gas projects, including gas-to-liquids fuels, or GTL, a secret process that uses cobalt to convert natural gas into clean-burning diesel fuel.
Qatar is also home to a large US military base.
The country also shares with Iran the world's largest natural gas field, estimated to hold 9 per cent of proven global gas reserves.