The 72-year-old had been charged with two counts of rape of the same woman in 2011, one in October and another in December. The district court found him guilty of the former charge, but cleared him of the latter. But on Monday the appeals court pronounced him guilty of both, locking him up for two years and six months.
Svea Court of Appeals said in a statement on Monday that it was of the view that the trial had established "beyond reasonable doubt that the accused was guilty of rape also on this occasion". It said it found the victim and several witnesses "reliable and that the evidence is sufficient for a conviction".
The trials heard that Arnault, who has insisted he is innocent, forced the woman – who was in a state of "intense fear" according to the prosecution – to have oral sex and intercourse in a Stockholm apartment on October 25th, 2011, and raped her during the night of December 2nd-3rd while she was asleep.
The appeals court also ordered Arnault to pay the victim 215,000 kronor ($24,000) in damages.
Nobel Literature Prize postponed
Arnault is married to a member of the Swedish Academy which selects the Nobel Literature Prize winner, with the scandal prompting the institution to postpone this year's award.
The Frenchman also ran the Forum club, a meeting place for the cultural elite and popular among aspiring young authors hoping to make contact with publishers and writers.
The revelations left the Academy, which had funded his club for years, deeply divided over how to manage their ties to him and his wife, poet Katarina Frostenson.
Six of the 18 members resigned or went on leave in the wake of the row, and several of them traded ugly barbs via the media.
In ruins and without a quorum to make key decisions (an additional two members had already resigned on previous occasions), the Academy postponed this year's Nobel Literature Prize, a first in 70 years.