Batting first, the Northerners amassed a healthy total of 125, with Riverina squad member and North skipper Charlie Paton a standout, scoring 42 before retiring.
Paton was well supported by Henry Knox (14 not out), Ben Dunmore (seven) and Jack Murray (seven).
Blake Marshall had a day to remember for South, snaring 6/18, including an elusive hat-trick.
Baxter Cowley (1/15 off five overs) restricted the run rate with a tight spell for South.
The South chase began slowly, and after 13 overs the team had crawled to 23.
Needing a boost in their run rate, big hitter Sam Pereira (24 not out) delivered, but ran out of partners.
Ethan Connolly was next best with the bat, scoring nine.
For the Northies, Paton was again in good form taking 3/8 with his spinners, being well supported by Ben Dunmore (2/6) and Harley Hicks (1/3).
Deniliquin North will move on to the next round, playing the winner of the Tocumwal vs Finley match.