David S. Smith, 53, of 2865 Chattahoochee Road was arrested Dec. 4 by Forsyth County Sheriff's investigators.
He has been charged with providing contraband to an inmate and distribution of a schedule 4 narcotic. A jail spokeswoman said bond has not been set.
Ronald Earl Young Jr., 26, an inmate at Phillips State Prison in Buford, faces one count of the same charge.
Authorities suspect the drug was Xanax, commonly used to treat anxiety.
Sheriff's Capt. Paul Taylor described the incident as unusual.
"That's not a call you get every day," he said.
Taylor said the arrest was made after a state inmate supervisor reportedly saw Smith give the drug to Young while the men were at the county roads and bridges department building.
"(Young) was working up there under guard and was approached apparently by Mr. Smith and Mr. Smith distributed this one tablet to him," Taylor said.
According to a sheriff's report, authorities were called Dec. 4 to the roads and bridges department, where Smith works, to investigate the incident.
Georgia Department of Corrections records show Young is serving time on marijuana charges.
Taylor was not sure how the charge against Young would affect his prison sentence.
It could not be determined what, if any, disciplinary action Smith faces from the county, or whether he's still employed.