Sinclair, 28, has scored 25 goals in his debut season as the Scottish champions chase a domestic treble.
He beat team-mates Moussa Dembele and Stuart Armstrong, as well as Aberdeen’s Jonny Hayes, to the award, which was voted for by his fellow professionals.
Celtic’s Kieran Tierney was voted young player of the year.
Celtic boss Brendan Rodgers was named manager of the year.
The former Liverpool boss, who won the League Managers Association prize in 2014, has not lost a domestic game since arriving in Scotland.
Parkhead striker Dembele made it four awards on the night for the club when his third goal in the 5-2 win over St Johnstone in February was voted goal of the season.
Hibernian’s John McGinn claimed the Championship player of the year award after the Scotland midfielder helped the Easter Road side win promotion and reach the Scottish Cup semi-finals.
Livingston’s Liam Buchanan won the League One player of the year award.
Shane Sutherland of Elgin City taking the League Two award.
The Scotland women’s national team also won a special merit award after reaching this summer’s European Championships.