"I appreciate Ian's decision and the backing he has handed me, Matthew and Pipey," Whitlow told the club's official site.
"The last month has been hard for me. I went on the list for not playing how I should have been and I have worked hard to improve my performances since."
36-year-old Whitlow has arguably undergone the biggest transformation since Mills' departure, turning in two of his best displays since arriving at Meadow Lane on a free transfer from Sheffield United in the summer.
The much-travelled defender - whose former clubs include Leeds, Bolton and Leicester City- has also been re-instated as captain after being temporarily stripped of the honour by Mills.