The win took Waikato to 22 points from 14 matches, two clear of Nelson who have played the same number of games, with two rounds of the regular season remaining.
It also ended North Harbour's four-match wining streak leaving the home side facing a road trip in the first round of the post season, almost certainly away to the fourth ranked team on June 17.
It was close throughout in a low-scoring encounter which saw the teams go into halftime level at 37-37.
The second half followed a similar pattern to the first with North Harbour unable to find the basket despite numerous chances in the face some heavy defensive pressure.
Mike Bell showed his class for North Harbour, scoring 20 points, snatching 11 rebounds and making three blocks.
Thomas Abercrombie led the scoring for Waikato with 19 points and also found time for eight rebounds, three assists and three blocked shots in a busy night.
