The 28-year-old former Celtic man, whose contract expired earlier this month, has made eight npower Championship appearances for the Robins this season and has impressed new head coach Sean O'Driscoll enough to be offered a fresh deal.
"Mark Wilson had a clause in the contract that he originally signed allowing for it to be extended," O'Driscoll told the Bristol Evening Post.
"He is still training with us and will be here until the end of the season."
O'Driscoll will watch fellow defender Matthew Bates train next week before deciding whether to offer him a new contract.
The ex-Middlesbrough player, whose deal ran out earlier this month, has been suffering from gastro-enteritis and has been unable to train.