Lauren Bell started with the ball for England as the West Indies slumped to another series defeat.
With the five matches already concluded, England look set to be swept in the series after a convincing 49-run win at the Kensington Oval.
After electing to bat first, England were restricted to 131-8 with Sophia Dunkley top scoring with 35 from 32 balls.
Katherine Brunt (24) and Charlie Dean (20) shared a 45-run eighth-wicket partnership to help England to 131 after they slumped to 86-7 after 14 overs.
Sheneta Grimmond and Cherry-Ann Fraser finished with three wickets apiece as the West Indies got a sniff for a first win of the tour.
But the innings response saw the hosts lose two wickets in the first over, with Bell taking the wickets of Aaliyah Alleyne and Rashada Williams for a wicket.
Bell had another career-best performance, this time finishing 4-12. She was supported by the spinners, with Sarah Glenn (1-16), Charlie Dean (2-16) and (2-13) all among the wickets as England bowled West Indies for just 86 runs.
Sophie Ecclestone also claimed a new women’s cricket record, with the 23-year-old taking her 56th international wicket this year – the most ever by a woman in a calendar year.
The win means England win 4-0 in the T20 series, ahead of the final game at the same ground on Thursday.
Sophie Ecclestone said: “I’m really loving this tour, the new head coach coming in has really changed things a bit and it’s been great to have everyone back together. After being in the Big Bash it feels great to be back in a England shirt.
“It was a bit of a difficult wicket today but playing spinners with Glenny [Sarah Glenn] and Deano [Charlie Dean] is great for me and great for the three of us, and I’m glad we’re doing well together. Deano obviously played a T20 in the Ashes and didn’t bowl a ball or field a ball, so I think it’s great that she’s shown how great she can be.”
“Looking forward to the World Cup, they are always amazing to be a part of and the event itself will be fantastic, I think the upcoming team we have now is fantastic and I can’t wait to see what we can do.
“Jon Lewis has been great for us, I think we needed someone to come in and freshen things up and be in a position to be able to go out and be positive and give everything to the team and not have any worries if it goes. error and leave everything out on the field.”