They sit one point ahead of Northern Districts, who beat Canterbury by 43 runs at Hagley Oval.
ND needed a brutish cameo from Brett Hampton to reach 274, with Hampton bashing 34 off 12 balls, including four straight sixes off spinner Tim Johnston.
English all-rounder Ben Stokes took his first wicket for Canterbury, but had less luck with the bat, being run out after facing one ball.
His partner involved in the miscommunication, Michael Pollard, went on to be Canterbury's main contributor, dragging them back from 79-5 to give the hosts a flicker of hope.
The opener scored his first century in 114 domestic innings, but when he fell for 119, Canterbury's chances disappeared with him, falling short to remain winless.
Canterbury are now the only team without a win, after Wellington claimed a five wicket victory to send Auckland to their first defeat.
An unbeaten 125 from Mark Chapman saw Auckland post 266-7 from 46 rain-affected overs, but Wellington had no problems chasing it down at Eden Park Outer Oval.
A rapid 117 from 91 balls from Stephen Murdoch did the damage, before Devon Conway's unbeaten 24-ball 43 saw them home with five overs to spare.