The New Zealand women's team, also known as the 'White Ferns', chased down the target in 15.5 overs after restricting Sri Lanka to 110 for six.
Captain Suzie Bates scored a run-a-ball 37 while opening the batting alongside Rachel Priest, who struck 28 off 26 balls at the Feroz Shah Kotla.
With Bates and Priest scoring at a brisk rate, it seemed Sri Lanka will go down without a fight.
However, some reckless play by the batsman gave a glimmer of hope to the Sri Lankans as New Zealand lost three quick wickets to slip to 77/3 after the openers had shared a 64-run partnership.
More From This Section
With the win, New Zealand maintained their 100 per cent win record against Sri Lanka in seven T20 Internationals.
Earlier, Sri Lanka made a solid start through openers Chamara Atapattu (17) and Yasoda Mendis (30) before losing their way.
Mendis struck some elegant strokes while batting alongside Atapattu as the two took the team to 39 for no loss in six overs.
Dilani Manodara (37) then joined Mendis and overtook the role of aggressor from the Sri Lankan opener.
Manodara brought the sparse crowd at Kotla to life by depositing Bates over long on for the first six of the game.
However, a flurry of wickets after the fall of Mendis left Sri Lanka struggling at 96/6 from a promising 82 for one in the 13th over.
While Mendis offered a simple catch at mid-wicket, Manodara was unlucky to have got run out.
The Lankan innings failed to get a move on thereafter with New Zealand putting up an impressive effort on the field.
Brief scores:
Sri Lanka: 110/8 in 20 overs (Yasoda Mendis 30, Dilani Manodara 37; Leigh Kasperek 2/19).