South Korea scored a fast-break goal through Darae Kim just before halftime and, while New Zealand battled hard, it simply could not find an equalising goal.
The Black Sticks had their best scoring opportunity from a penalty corner with 16 minutes remaining but Anita Punt's powerful drag flick went just wide of the right post.
With one win and one loss so far at the tournament, the next three pool games against the Netherlands, Australia and Japan become extra important with the semifinals looming.
Head coach Mark Hager said the loss was disappointing but his side would now regroup and focus on performing well in its next clash.
''The way we lost was the most disappointing thing; we had no fight in us today. They outplayed us and deserved to win the game,'' he said.
''We didn't create enough opportunities, didn't move the ball well and we didn't win enough one-on-one contests.
''In the end it came down to one error on a sideline free hit where we didn't cover properly. We'd spoken about it before but we weren't diligent enough about it and they scored an opportunist goal.
''It's disappointing but you've got to move on and we now need to get six or seven points from our final three pool games otherwise we're going to be in trouble.''
The Black Sticks Women play their third pool game against the Netherlands in front of a sold-out stadium of 15,000 tomorrow.
The Black Sticks Men were to play South Africa in their second pool B game this morning.
In other women's pool A results yesterday, Australia edged Japan 3-2 to remain unbeaten while the Netherlands thrashed Belgium 4-0.
