Wellens returned to the club from Leicester City in the summer and has played 24 times this season in the South Yorkshire club's return to the Championship, collecting eight yellow cards.
The 33-year-old has been linked with moves to QPR and Leeds but will now stay at the Keepmoat Stadium until the end of the 2014-15 season.
Wellens said: "Obviously it's taken a while and talks have been on going but I'm pleased to have got something sorted with the club. Hopefully now we can just concentrate on trying to stay in the league and get some good results."
Chief executive Gavin Baldwin said: "The owners and manager have worked incredibly hard to ensure we manage to keep Richie at the club long term.
"This is great news for everyone involved and a clear signal of the owners' intent for the future of Doncaster Rovers."
Wellens, who started his career at Manchester United, played for Blackpool and Oldham Athletic before his first spell with Doncaster began in the summer of 2007.
He left Rovers to join the Foxes for a fee of £1.2 million in 2009 before rejoining Doncaster last summer in a short-term deal after a loan spell with Ipswich Town.
Meanwhile, midfielder James Harper has left the club by mutual consent after finding first-team opportunities limited this season.