Pollard battered Ireland's bowlers for eight fours and five sixes in a 55-ball assault and then got rid of Irish dangerman Kevin O'Brien with his diving take at long-on to help West Indies to a third successive win in Group B.
It puts West Indies on the brink of a quarterfinal place. Pollard's power-hitting had sent his team to 275 all out in 50 overs, alongside 107 from opener Devon Smith.
Ireland was all out for 231 in its chase, despite half-centuries by Ed Joyce (84) and Gary Wilson (61).
Joyce and Wilson had shared a 91-run stand, but they were dismissed in quick succession and Ireland faded away.