Leonard, who led the league with 2.3 steals per game this season, received 37 first-place votes and 333 points, while Golden State Warriors forward Draymond Green came second with 317 points and Los Angeles Clippers center DeAndre Jordan finished third with 261 points.
"It feels great," Leonard told ESPN. "Growing up as a kid, you're watching these players and you want to become who they are or get the accolades that they have. It just shows that hard work pays off."
Leonard also became only the third player in NBA history, after Michael Jordan and Hakeem Olajuwon, to win the Defensive Player of the Year award and be crowned NBA Finals MVP, which he accomplished last season.
Despite finding himself amongst the greatest players to have ever stepped foot on the court, Leonard believes that this is just the beginning.
"I'm still young, I feel I can get a lot better," he said. "I don't know, I'm just going to keep striving and trying to help my team win the game, hopefully I'll keep getting better."
When asked who he credits most for his Defensive Player of the Year award, Leonard had no hesitation in naming head coach Gregg Popovich and team-mate Tim Duncan.
Despite having played 18 seasons and performed fairly consistently in all of them, Duncan has never won the Defensive Player of the Year award.
However, Leonard made it clear that the veteran power forward helped transform him into the player he is today.
"(Duncan's) focus, his mindset going into every game," Leonard said. "Playing both ends; wanting to shut his opponent down, just playing great team defense also.
"When a guy drives by me, he is there for the help side in the box so he doesn't get deflections and making the passes harder. Just learning his work ethic and his mindset going into every game (helped my development)."