Embiid told reporters the "referees f--king sucked" before he stormed off the podium.
Embiid's frustration may have stemmed in part from a missed foul call in the final minute while Philadelphia trailed by two points.
Celtics center Al Horford appeared to hit Embiid's arm on the play, but the officials didn't blow the whistle. Marcus Smart made a layup on the following possession to put Boston up 108-104 with 23.9 seconds remaining.
Embiid may also be frustrated because of his ongoing struggles against Horford and the Celtics. The Sixers All-Star finished with 23 points and 14 rebounds in the loss, but he shot 3-of-12 through three quarters.
Philadelphia remains unable to get over the hump against its Atlantic Division rivals. The Celtics are 3-0 in head-to-head matchups with the 76ers this season. Both teams have matching 36-21 records with one game remaining until the All-Star break.