After the Black Sticks broke downfield and secured a penalty corner late in the third quarter, experienced drag flicker Kane Russell ripped a shot into the top netting of the goal to give New Zealand an almost unassailable lead.
Into the final quarter and needing four goals, the Koreans pulled their keeper and were rewarded with several penalty corners.
The visitors dominated possession through the last quarter but the Black Sticks held their nerve to book their place at the Tokyo Olympic Games.
The side now take a break after a long season which started in January with the inaugural FIH Pro League, before returning to the turf at the start of February for season two of the Pro League.
The Black Sticks will begin their Olympic year against world champions Belgium at the new National Hockey Centre in North Harbour.
Black Sticks Men 3 (Stephen Jenness 16', Sam Lane 23', Kane Russell 42')
Korea 0