Harden becomes the third ever Rocket to claim the award following Moses Malone (1979 and 1982) and Hakeem Olajuwon (1994).
Harden is only the second player in National Basketball Association history to win the MVP and Sixth Man of the Year awards in their career (Bill Walton was the other).
Daryl Morey of the Rockets earned the NBA's Executive of the Year Award after assembling a team that finished first in the Western Conference.
Harden led the league in scoring, 3-pointers and 50-point games with four.
"But it seems that what we have today is a system where you don't want players to say anything at all", he said.
While a number of other honors were handed out at the 2018 NBA Awards Show on Monday night, the main event was scheduled for the end. Unfortunately for him, his incredible playoff run didn't factor into the voting (since MVP is a regular-season award).
"Can't look in the rear view mirror", Casey said backstage.
Lou Williams of the Los Angeles Clippers took Sixth Man honors. Casey also coached the Eastern Conference in this year's All-Star Game. Houston established a new franchise record for wins with 65 against only 17 losses.
Harden's teammate, Chris Paul, popped up among reporters backstage and asked Harden how many bottles of liquor Rockets CEO Tad Brown would have to buy at the next location.
Those facts were not lost on two-time MVP victor Stephen Curry, as he took to Instagram to wonder if the man who drafted those players for the Thunder, Sam Presti, was getting an MVP award too.
The guard averaged 15 points, eight rebounds and eight assists, joining Hall of Famer Oscar Robertson as the only rookies to post those numbers in a season.