He is the third Dons players to be hit with injury in recent weeks.
Jonny Hayes suffered hamstring damage in the defeat by Inverness Caley Thistle last month.
Then top scorer Adam Rooney was ruled out until mid-April after suffering a thigh injury on the eve of last Saturday’s clash with St Johnstone.
Aberdeen says Pawlett is likely to be out “for some time” after breaking his arm in the midweek win over Dundee United.
A statement released by the Pittodrie club said: “Aberdeen can this afternoon confirm that midfielder Peter Pawlett suffered a broken arm during the 1-0 victory over Dundee United at Tannadice on Wednesday night.
“Peter, who was making his 191st appearance for the club, was substituted during the game after 62 minutes. He is likely to be out of action for some time.”
There was better news on Hayes, however, with the Dons hoping he will be fit enough to return to action against Partick Thistle at Firhill on Tuesday evening as Aberdeen seek to close the gap on Celtic at the top of the Premiership to a single point.
Aberdeen also confirmed that they are to appeal the yellow card given to Graeme Shinnie against United when left back was booked for simulation.
Simulation is the only offence for which the awarding of a yellow card can be appealed against.