The challengers got off to a flying start, capitalising from some poor discipline from the hosts to opening the scoring through centre Daniel Rona.
While Tasman hit back with a penalty, before a converted try and two penalties saw Taranaki run out to a 20-3 lead.
Taranaki were defending well and getting players to the breakdown quickly, allowing them to apply pressure and make the most of their attacking opportunities.
Tasman showed glimpses toward the back end of the first half and finally broke through the Taranaki defences with Jack Gray scoring in the corner.
Taranaki led 23-8 at halftime, but Tasman closed the gap soon after the restart when lock Tim Sail went over.
There were plenty of opportunities both ways in the second half as the game opened up, with Taranaki pulled away against with tries through Jacob Ratumaitavuki-Kneepkens and Rona, before Tasman closed the gap to within six points with 10 minutes to play.
But a late try through Adam Lennox was enough to secure Taranaki another Shield reign.
The win also finalised the draw for the quarter-finals, beginning with Wellington hosting Counties Manukau on Friday night.
The battle of the bays sees Bay of Plenty meet Hawke’s Bay in Tauranga on Saturday afternoon, with Taranaki taking on Waikato in New Plymouth that night. The final match of the round sees Tasman host Canterbury in Blenheim.
Tasman 29 (Jack Gray, Tim Sail, Ryan Coxon, David Havili tries; William Havili 3 cons, pen)
Taranaki 42 (Daniel Rona 2, Michael Loft, Jacob Ratumaitavuki-Kneepkens, Adam Lennox tries; Josh Jacomb 4 cons, 3 pens)
HT: 8-23
