Ashwin picked 24 wickets and scored a century against England in month of February to win the award.
India won the series 3-1 and also qualified for the final of the World Test Championship and is likely to face New Zealand at the Ageas Bowl in Southampton from June 18-22.
Ashwin ended the series with 32 wickets and 186 runs to his name, out of which 24 wickets and one century came in the month of February for the Indian team. His ton was his fifth in Test cricket and was hit on his home ground of MA Chidambaram Stadium in Chennai.
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Ashwin also picked a five-wicket haul in one of the innings, making it the third time he had achieved the feat of a century and a fifer in the same Test.
He also became the second-fastest bowler in history to 400 Test wickets, behind only Sri Lanka's Muttiah Muralitharan.
"Ashwin was the unanimous choice to win in the men's category for February and garnered the most votes in the fan vote," the International Cricket Council (ICC) said in a statement.
"Ashwin's consistent wicket-taking, even in helpful conditions have helped to put his team ahead in a very important series. His century in the second Test was as critical as it came when England were trying to claw their way back into the match. That knock ensured that India shut the door on the opposition," Ian Bishop - representing the ICC Voting Academy - was quoted as saying.
Apart from Ashwin, England’s Tammy Beaumont also won the ICC Women’s Player of the Month for February 2021. She won it for scoring 231 runs in 3 WODIs against New Zealand in Christchurch and Dunedin. She made 71, 72* and 88* in the three matches, helping England win the series 3-0.