Aubameyang was sent off midway through the second half of Arsenal's 1-1 draw with Crystal Palace on Sunday (AEDT) after lunging in on Max Meyer.
The Arsenal captain was initially booked for his challenge, but VAR directed referee Paul Tierney to change his decision to a straight red.
Arsenal appealed the red card, but – in his news conference to preview Saturday's clash with Sheffield United – Arteta revealed Aubameyang will have to serve his suspension.
"That has been confirmed that he will be suspended for three games, so we are not going to have him for three fixtures," Arteta told reporters.
"It is a big shame, it is a big loss for us because as well, we know it was not his intention. But he mistimed the tackle, made the decision and we have to accept it.
"He was very sad after the game, disappointed he left the team with 10 men. It was an action which was completely accidental in my opinion.
"For me he has been superb, working so hard, scoring goals and probably has been the most important player of the team so to lose him is really bad news for us."
Aubameyang, who will miss Saturday's match with the Blades, a derby clash with Chelsea and an FA Cup tie against Bournemouth, scored the opener at Selhurst Park before Jordan Ayew drew Palace level.
The former Borussia Dortmund striker – who shared the Premier League Golden Boot along with Sadio Mane and Mohamed Salah last season – has scored 14 times in the top flight so far this term.