The 28-year-old joined the Spireites on a one-year deal in June and has scored seven goals in 24 appearances.
In October Evans was found not guilty, following a retrial, of raping a 19-year-old woman in a hotel room in 2011.
He was initially found guilty in 2012 and served two-and-a-half years of a five-year prison sentence, but his conviction was quashed in April 2016.
Wales international Evans told the club website: "I'm really pleased to have got this sorted out.
"I want to play well and score as many goals as I can between now and the end of the season to help us get out of the relegation zone."
Chesterfield, who are set to appoint former Coventry City manager Tony Mowbray as their new boss, are in the League One relegation zone on goal difference.
Chesterfield striker Ched Evans has signed a 12-month contract extension with the League One club.