The sexual contact between Jennifer Ann Baran, 33, of Chester, and the inmate occurred between January and April 2012.
Baran's arrest came more than a year after Henrico Internal Affairs opened its investigation into her actions.
The investigation began in May 2012 when deputies discovered a Henrico jail inmate had a cell phone while behind bars, according to Henrico Undersheriff Carlos Talley.
When investigating how the inmate got the phone, deputies discovered love letters Baran wrote in the inmate's cell. The Henrico Sheriff's Office turned its evidence over to Virginia State Police for further investigation.
Baran, who resigned from the Sheriff's Department in May 2012, was arrested and placed in jail where she once worked. She has since been transferred to Pamunkey Regional Jail.
Investigators believe for nearly four months in early 2012, Baran engaged in sex acts with the inmate.
At the time she was in charge of the jail laundry room, and investigators say that's where the illegal activity took place.
Talley says because technically the inmate is a victim, they're not releasing his name.
"It's our duty and responsibility to provide a service for these inmates and a deputy having sex with them compromises things," said Talley.