Taieri muscled up in the forwards to claim a deserved breakthrough win of the season in front of an appreciative home crowd at Peter Johnstone Park.
Pirates dominated the scrum, where veteran props Shane Parata and Daniel Johnson showed all their guile and power, and won its share of line-out ball.
But Taieri's edge was in the loose forwards, where No 8 Charlie O'Connell and flankers Jeremy Corliss and Nathan Young hunted the ball with aggression and precision.
The sides went try-for-try in an entertaining first half, highlighted by the first of Taieri fullback Jared Campbell's two tries, scored after a deft behind-the-back pass from Todd Ford, and a 50m breakaway try from Pirates winger Jeremy Cave.
Taieri took control of the game five minutes into the second half when O'Connell appeared with the ball from a ruck and Campbell was on his shoulder to score.
Pirates struck back late with a try to replacement lock Brad Ross and had a couple of reasonable opportunities to steal the win, but Taieri's resolve held.
The backs were evenly matched, with second five-eighth Andrew Reid taking intelligent options for Taieri and both Cave and fullback Kieran Fowler looking potent at times for Pirates.
Taieri 25 (Jared Campbell 2, Jeremy Corliss tries; Hayden Parker 2 conversions, 2 penalty goals), Pirates 20 (Warren Kearney, Jeremy Cave, Brad Ross tries; Kieran Fowler conversion, penalty goal).
Halftime: Taieri 17-15.
Referee: Liam Scanlon.
