Graaback, who started the 10km cross-country course 42 seconds behind after coming sixth in the ski jump, won the event in a time of 23 minutes 27.5 seconds, pipping countryman Magnus Moan by 0.6 seconds.
Germany's Fabien Riessle took the bronze, crossing the line 1.6 seconds behind Graabak.
Eric Frenzel, who won the normal hill event, started first in the cross-country section after landing the biggest jump but could not shake off the after-effects of a virus and ended in 10th place.
(Reporting by David Ljunggren; editing by Peter Rutherford)
