South African captain Graeme Smith smashed 61 off 43 balls as the home side raced to 84 without losing a wicket after they were sent in.
But South Africa collapsed dramatically to be bowled out for 133 in 19.3 overs, with slow-medium bowler Nathan Astle and off-spinner Jeetan Patel taking three wickets each.
Smith took full advantage of the opening seven overs of fielding restrictions as he thrashed the faster bowlers for ten fours and a six. He and opening partner Jacques Kallis seemed to have laid the foundation for a massive total.
The introduction of Astle and Patel brought New Zealand back into the contest. All ten wickets fell for 49 runs in ten overs.
New Zealand also got off to a good start, with captain Stephen Fleming and Astle putting on 37 in five overs before Astle was bowled by the first ball sent down by first-change fast bowler Andre Nel.
A second wicket fell five balls later when Hamish Marshall was caught behind off Nel.
Swing bowler Charl Langeveldt claimed the key wicket of Fleming in the next over when the New Zealand captain slashed a catch to Albie Morkel at gully.
Craig McMillan and Scott Styris steadied the innings with a stand of 34 and the match was effectively settled when tall left-hander Jacob Oram hit sixes in successive overs off Nicky Boje and Albie Morkel. Oram finished with 23 not out.
The match is a one-off prelude to a five-match 50-overs international series which starts in Bloemfontein on Sunday.
Scoreboard
SOUTH AFRICA:
G.C. Smith c and b Astle 61
J.H. Kallis b Patel 20
H.H. Gibbs lbw b Patel 9
J.M. Kemp c and b Astle 8
M.V. Boucher b Astle 4
S.M. Pollock c Fleming b Adams 0
A.G. Prince run out 5
A. Morkel c McCullum b Patel 11
C.K. Langeveldt b Bond 2
M. Ntini b Bond 5
A. Nel not out 0
EXTRAS (B-1, LB-2, W-1, NB-4) 8
TOTAL (19.3 overs) 133
FALL OF WKTS: 1-84, 2-90, 3-99, 4-105, 5-106, 6-110, 7-115, 8-121, 9-129.
BOWLING: Bond 3.3-0-25-2; Mills 4-0-38-0 (2nb, 1w); Adams 4-0-27-1; Astle 4-0-20-3; Patel 4-0-20-3 (2nb).
NEW ZEALAND:
S.P. Fleming c Morkel b Langeveldt 31
N.J. Astle b Nel 10
H.J.H. Marshall c Boucher b Nel 3
C.D. McMillan c Nel b Boje 15
S.B. Styris b Langeveldt 24
J.D.P. Oram not out 23
B.B. McCullum not out 17
EXTRAS (B-1, LB-3, W-3, NB-4) 11
TOTAL (for five wkts, 18 overs) 134
FALL OF WKTS: (details not available).
DID NOT BAT: J.A.H. Marshall, K.D. Mills, A.R. Adams, S.E. Bond.
BOWLING: Pollock 3-0-16-0; Ntini 2-0-21-0; Nel 4-0-19-2; Langeveldt 2-0-14-2 (2w); Boje 4-0-27-1; Morkel 2-0-13-0; Smith 1-0-20-0 (4nb).
RESULT: New Zealand won by five wickets.—AFP