The 26-year-old actor has told friends he does not want to see or speak to Stewart, 22, after her fling with married film director Rupert Sanders, 41.
But the "Twilight" co-stars, who play couple Bella Swan and Edward Cullen in the film, have been told by producers they must attend the November premiere of the final film, reported Sun online.
"They are contractually obliged to be pictured side by side on the red carpet. RPatz is in pieces but the 'Twilight' love triangle storyline is nothing without him and Kristen. It is eating him up that he has no choice but to see her again because of work. His humiliation is total," a source said.
Pattinson moved out of the Los Angeles, California mansion he shared with Stewart after he discovered her affair with father-of-two Sanders.
Both Stewart and Sanders, who met on the set of "Snow White and the Huntsman", have publicly apologised.