Media reports Judge-Executive Davie Greer appointed deputy Kent Keen to the position and he was sworn in on Monday.
Former Barren County Sheriff Chris Eaton resigned last week, a day before being sentenced to 18 months in prison for persuading two deputies to write false incident reports in an FBI investigation of an alleged beating during an arrest.
The 42-year-old Eaton, of Glasgow, was acquitted during his trial in May of using excessive force but convicted of witness tampering.
Greer says she weighed her decision carefully before making the announcement.
Barren County Deputy Bobby McCown said Keen is known for his integrity.