Lee had just entered the final 12 months of his existing deal but he is set to sign a two-year extension which will keep him at the Proact Stadium until the summer of 2018.
“He has not actually put pen to paper yet but Tommy has shook hands on a new contract with (chief executive) Chris (Turner) and I am really pleased about that because I think he is the best goalkeeper in our division,” Chesterfield manager Dean Saunders said.
“Any team I ever played in that was any good, or any good team that I have managed, always had a really good goalkeeper.
“I believe he is worth somewhere between 10-15 points a season for us so we should all be really pleased that he has agreed to stay here for another couple of years.
“He is a proper professional. He wants to win, he trains really hard every day and the club should be proud of him.”
Lee came through the youth ranks at Manchester United and had spells with Macclesfield and Rochdale before signing for the Spireites in 2008.