Andrew Dickson (1-22), Nathan Hoobin (0-10) and Zac Farmer (1-31) all bowled with merit.
The Wanganui batsmen started slowly at the crease, but eventually built a 65-run partnership in 17 overs between Ben Louden (21) and Charlie Lourie (25), in a new role as opener.
Lourie's dismissal saw the middle order begin to creak with wickets falling regularly, including three run outs.
Having come in at No5, Hunter Morrison showed some maturity by holding the innings together with 29 off 48 balls, as wickets tumbled around him.
He was dismissed off a stumping in the 39th over with the team needing three more runs for victory, which was achieved with only four balls to spare.
Taranaki sent down 21 runs worth of wides among 35 extras did not help their cause, given Wanganui conceded only 19 when bowling.
"A hard fought victory that our batsmen made more difficult than it should have been," said Drew Morrison.
"Lessons to be learnt would be the large number of 'dot' balls in our innings."