The Wales international frontman has played a major role in firing the Lancashire club to the brink of a Premier League return with 20 goals in 39 Championship games.
But Vokes ruptured his anterior cruciate knee ligament in Saturday's 2-0 home defeat against leaders Leicester City, a result that severely dented Burnley's title tilt.
Vokes joins fellow striker Danny Ings - who has 19 league goals to his name in 2013-14 - on the sidelines, along with right-back Kieran Trippier - arguably the club's three best players.
The squad depth at second-placed Burnley - who are nine points clear of QPR in third - will now be tested to the limit over the last seven games of the season.
Burnley boss Sean Dyche told the club's official website: "Sam has had a great season and I am sure you will join us all in supporting him during his recovery.
"As ever, our team mentality remains focused and this represents another opportunity for someone to come and make a continued contribution in the closing weeks of the season."
