Opting to bat, the Misbah-ul Haq led side could manage only 139 for eight in the wake of some controlled bowling from the Otago bowlers.
Pacers Ian Butler (2/23), James McMillan (2/24) and James Neesham (2/26) all bowled well with only Misbah making a significant contribution with 46 off 34 balls.
In reply, McCullum hit an unbeaten 83 from just 65 balls studded with nine fours and two sixes, besides sharing a 41-run stand for the second wicket with Hamish Rutherford (25) before putting on an unbeaten 101-run partnership with Derek de Boorder (30 not out).
While McCullum adopted a cautious approach at the start, left-handed Rutherford attacked the bowling, hitting a six each in three consecutive overs to set it up for the winners.
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Saeed Ajmal, however, saw Rutherford off having scored quickfire 25 off 12 balls that included a boundary and three sixes. But McCullum firmly held on to his wicket and patiently continued in the able company of De Boorder.
Once they got set, the two right-handers cut loose and McCullum looked in devasting form as he dismissed any loose deliveries out of his presence.
McCullum got a life when he was dropped on 42 off Imran Kahlid's over. He capitalised on the advantage and it just was a matter of time before he steered his team to 142 for two in 17.5 overs.
De Boorder's unbeaten 30 came off 28 balls (2X4, 1X6).
Barring spinner Saeed Ajmal, who gave away 23 runs in alloted four overs for a wicket, the rest of the Wolves bowlers failed to contain McCullum.