Chesterfield manager Lee Richardson has maintained a strong relationship with Nottingham Forest by luring young defender Brendan Moloney away from the City Ground.
Moloney has signed on a month's loan and is the second Forest player to move to Saltergate after team-mate Felix Bastians joined earlier in the season.
Republic of Ireland under-19 international Moloney is expected to be available for the Spireites trip to Brentford this weekend.
"We are delighted that Brendan is joining us at this time when we need some extra defensive cover," Richardson told the club's official website.
"We don't want to get caught out due to any additional injuries or suspensions during a busy January."
The 18-year-old has been an essential part of Forest's current reserve side, and has represented the first team twice so far this season.
Last seasons 'Nottingham Forest Young Player of the Year' has signed a contract - but the paperwork is not expected to clear until Friday.