The incident occurred with the Los Angeles Lakers down by 12 points in the third quarter, with James ejected for a Flagrant 2 foul along with Stewart.
Stewart reacted angrily after an errant James’ elbow at a free-throw left his right eye bloodied, before the Pistons center repeatedly charged at the Lakers star amid wild scenes.
The Lakers went on to storm back with a 37-17 fourth quarter to win 121-116 but James’ ejection was the talking point.
Lakers teammate Anthony Davis had defended James after the game, insisting that “everybody in the NBA knows he’s not a dirty guy”.
But the NBA confirmed on Monday that James had been sanctioned with a one-game ban for “recklessly hitting”.
Stewart was handed a two-game suspension for “escalating an on-court altercation by repeatedly and aggressively pursuing” James.
It is the first suspension in James’ 19-year NBA career. The two sides are due to meet again on Sunday, with both suspensions to be completed by then.
Lakers head coach Frank Vogel added: “It was unfortunate contact. (LeBron) had an elbow to the ribcage, which was a foul and he was trying to shed the contact, and he had incidental contact.
“It was obviously enough for a Flagrant 2, but the reaction was what it was, and I think our guys did a good job protecting a teammate but not trying to escalate.”