He blasted 172 off 76 balls in Australia's tri-series match against Zimbabwe, passing his previous mark of 156.
Finch shared a 223 run opening partnership - also a T20I record - with D'Arcy Short as Australia posted 2-229.
Finch was eventually dismissed hit-wicket. His innings included 16 fours and ten sixes.
The 31-year-old fell just three runs short of West Indian Chris Gayle's highest Twenty20 score of 175, which he hit in the 2013 Indian Premier League.
Finch has hit 398 runs in T20 internationals this year, at an average of 199.
He has only been dismissed once in matches against England, New Zealand and Pakistan this year, notching scores of 20no, 36no, 18no, 84 and 68no before his record-breaking innings against Zimbabwe.