The 22-year-old was handed a six month jail sentence, suspended for two years, after admitting to an assault on a woman in a bar in Bawtry last February.
The Rovers hierarchy acted swiftly, handing an immediate suspension to the right back, who will not be a part of the squad to travel to face Portsmouth this weekend.
Mason will be given a hearing next week to determine whether or not he will have his contract terminated by the club.
In such circumstances players are entitled to representation from the Professional Footballers Association (PFA) and it is understood the delay in Mason’s hearing is due to a lack of availability of a representative.
A statement from Rovers read: “Doncaster Rovers suspended Niall Mason on Tuesday afternoon and are investigating all matters in line with internal procedures and EFL contractual requirements following his conviction for sexual assault at Sheffield Crown Court.
“Mason had insisted he was innocent of the charge since the allegation was initially made, and the club had proceeded on that basis under the principle of innocent until proven guilty.
“No one from the club will make any further comment until the conclusion of this process.”
Mason has made 119 appearances for Rovers since joining from Aston Villa, initially on loan, in August 2016.
His current contract is set to expire in the summer.