The 24-year-old Pollard hit eight sixes and five fours in his 70-ball innings after Australia had won the toss and chosen to bowl.
It was the West Indies' highest score at the picturesque ground.
Pollard brought up his second ODI century in emphatic fashion with a huge six over midwicket in the final over off Brett Lee.
West Indies clobbered 145 runs off the last 12 overs with veteran quick Lee finishing with figures of 2 for 72 -- 23 of those runs coming off the last over of the innings.
Openers Johnson Charles (37), playing on his home ground, and the recalled Adrian Barath (41) gave the West Indies a solid foundation with a first-wicket stand of 56 by the 11th over.
The five-match series is currently tied at one win apiece after the first three matches in St Vincent.
Australia won the first by 64 runs before West Indies won by five wickets in a rain-affected second match on Sunday.
That win ended the West Indies' miserable run of 15 defeats in 16 one-dayers against Australia. The third ODI ended in a thrilling tie.
Australia made two changes to their team, bringing in batsman Peter Forrest and fast bowler Ben Hilfenhaus, who will play his first game on tour, for all-rounder Daniel Christian and offspinner Nathan Lyon.
West Indies called up Barath in place of Kieran Powell in their sole change.
Copyright AFP (Agence France-Presse), 2012