Faizullah Khan, a reporter for Karachi-based ARY News, was arrested in eastern Nangarhar province in April.
Khan was also accused of spying but a three-judge panel dropped espionage charges and jailed him for illegally entering into Afghanistan, The Express Tribune reported.
Some media reports have suggested Khan was on an assignment to interview Taliban leaders as part of his professional duties.
An appeal against the conviction will be filed in an Afghan High Court, the report said.
"The embassy will continue efforts to help the Pakistani journalist while using all legal options," the spokesman said.
Pakistan and Afghanistan are considered dangerous regions for journalists due to poor safety and security concerns. Also attacks on media professionals are a recurring feature in the regions.
