The academy badly needs new members to rebuild its ranks after a scandal this Spring caused several members to resign or be voted out.
The 18-member board selects the winner of the Nobel Prize for Literature but can only do so if it has enough active members.
But the scandal, involving a photographer who had close ties with the academy and was convicted of rape this week, forced the board to postpone this year’s Nobel Prize in Literature as it seeks to rebuild public trust in its work.
King Carl XVI Gustaf, the academy’s patron, approved the appointments on Friday. Both Mossaed and Runesson will take up their posts starting December 20.