Grant, who has 11 clean sheets to his name this term, took home the overall award after winning favour with four of the Clarets' nine individual supporters' clubs.
Three chose to honour free-scoring frontman Austin, also the recipient of the goal of the season gong for his superb winner at Charlton, while skipper Jason Shackell and winger Ross Wallace were the picks in Earby and Rossendale respectively.
Kieran Trippier received a special recognition award to mark his inclusion in the PFA's Championship team of the season.
Addressing those in attendance at the end of the evening, Burnley boss Sean Dyche said: "I've been learning since I've been here about the culture and the history of the club, and the supporters - and the demands of the supporters
I must say. It's an interesting journey but we do appreciate and value the support."