A pair of run outs also helped their cause as did some good glove work from wicketkeeper Luke Trigg, who took four catches.
After losing Chamod Peiris (6) early, Northland consolidated through Cullen Lowe (24), Hamish Kidd (23) and Liam Wewege (16).
But just as it looked good for the Northlanders, Coastlands' leg spinner Iman Singh (3 for 15) removed Lowe, Kidd and Wewege.
Singh and Joshua Healy-Ormrod, who took one wicket for just two runs in his three overs, turned the screws on Northland and ultimately kept them six runs short to give Coastlands the win.
Northland had no time to dwell on the loss as they were matched up with Waikato Valley shortly after the conclusion of their first match.
Bowling first, Northland struggled to keep right on top of Waikato Valley for the first 15 overs, but they never let them get into a commanding position.
Waikato Valley had the chance to do some damage with 88 runs on the board and eight wickets in hand with five overs to go, but Kidd (2 for 15) pegged them back as they limped to 110/6.
Caleb Boswell-Smith (37 not out) and Quinn Pooley (41 not out) then helped Northland romp home with six wickets to spare.