Chasing 192 for victory on Sunday night, New Zealand started slowly and lost opener Finn Allen in the second over, before Seifert grabbed the match by the scruff of the neck.
The 31-year-old belted five sixes and 11 fours en route to a knock of 93, but was unable to complete a first T20I century after a thick inside edge on a Nitish Kumar Reddy delivery crashed into his leg stump.
New Zealand were taken over the finish line by Glenn Phillips, whose 65 not out made him the highest-scoring batter ever in a bilateral T20I series with 341 runs, bettering England player Phil Salt's previous record of 331.
"(Having that) calm and the composure, it's a nice feeling," Phillips said.
"When you go out there with a clear mind and just try to play each ball on its merits and go out there and try and be a bit more of the hunter and a little less of the prey.
"Spin was going to be the type of bowling that needed to be taken down. Obviously we saw the Indian boys do it to us, and they did it very effectively."
The win also put a degree of respect on the series scoreline, after India had won the first three matches to seal the series.
After being put in to bat earlier on Sunday, India were struggling at 2-19 before a 93-run partnership between Shreyas Iyer (50) and Ishan Kishan (61) laid the foundation for a decent total.
Fast bowler Adam Milne was the best of New Zealand's bowlers with four wickets, while Nathan Smith and Blair Tickner had two apiece.
The sides will now turn their focus to one-day international cricket, with Eden Park in Auckland to host the first ODI of the five-match series on Wednesday.
