The win against West Indies in the final at Lord's on Saturday improved New Zealand's rating in the official ODI table from 112 to 113, the same as South Africa.
The Black Caps now remain narrowly behind South Africa in third spot when the ratings were recalculated to three decimal places, the ICC said in a release in London.
This is New Zealand's highest rating and is the closest South Africa has been to losing their grip on the second spot since the official ODI table was introduced in October, 2002.
The side entered the NatWest series in fourth place with 109 points and was the one of the participating teams to improve its rating during competition.
Hosts England failed to reach the final and their points have fallen from 105 to 101, while the West Indies' rating has slipped from 102 to 101. The teams remain in seventh and eighth position respectively.
India are in the fifth position with 107 points.
The annual update of the ICC Test and ODI championships will take place at the end of this month.
Australia have a healthy advantage at the top of both tables but second-placed South Africa will be looking nervously over their shoulder in both forms of the game.