Thisara Perera blazed his way to a maiden international ODI century but could not prevent New Zealand from sealing a series victory with a game still to play.
The Black Caps seemed to be cruising having reduced Sri Lanka to 7-128 as they pursued 320 to level the series at Mount Maunganui, but Perera's onslaught gave them a real fright.
The bowling all-rounder was dropped en route to a remarkable 57-ball ton and then again shortly after reaching the milestone, but he was eventually last man out for 140 from 74 deliveries after shovelling Matt Henry to long-on.
Despite his thunderous efforts, the tourists were all out for 298 as they succumbed to a 21-run defeat to the Kiwis, who claimed an unassailable 2-0 lead.
Earlier Ross Taylor (90) and Colin Munro (87) laid the platform for Jimmy Neesham to propel New Zealand to 7-319 with a blistering 64 from 37 balls.
