Welcker returned to Giessen in 1808, and resuming his school-teaching and university lectures was in the following year appointed the first professor of Greek literature and archaeology at that or any German university. After serving as a volunteer in the campaign of 1814 he went to Copenhagen to edit the posthumous papers of the Danish archaeologist Georg Zoega (1755–1809), and published his biography, "Zoegas Leben" (Stuttgart, 1819).