The Wanganui batters took an aggressive mentality into their chase and reached 101-2 in the 11th over.
Harry Godfrey played some beautiful shots while top scoring with 46 off only 31 balls.
A bad start with the bat cost the Wanganui Under 12s in their two-wicket loss.
Captain Shaun O'Leary elected to bat first, but the team collapsed to 34-7 after 15 overs. It was left to Carter Hobbs (29no) to salvage something with Andrew Dickson (9) and Adam Beard (11) providing support, as Wanganui were all out for 97.
In a carbon copy, Wanganui needed wickets and Dickson delivered by getting five scalps to finish with 5-17 from his six overs.
Having Manawatu at 30-6, Wanganui had regained momentum, but a 41-run partnership helped Manawatu get through to the end despite losing a couple more wickets.
Fellow bowlers Daniel Burgess (1-10), Oscar McVerry (1-10) and O'Leary (1-14) got scalps in the close defeat.
The Under 11 development team got home with three balls to spare to win a three-wicket thriller.
Manawatu compiled a tough 160-4 from their 35 overs, with Joshua Allpress taking 2-16 from his four overs while left arm spinner George Pearce gave up only four runs from his four overs, including two maidens.
The two allrounders Allpress and Pearce then combined for a crucial 94-run opening partnership, Allpress scoring 48 and Pearce 28.
Hunter Gibson kept the momentum going at No3 with 17, before nerves crept in and the Wanganui middle order had to work hard to get through to the well-earned victory.
The Wanganui age group sides take on the Wairarapa teams in Masterton this weekend.