The elk was so badly injured by the fall that authorities were required to put it down, reports broadcaster NRK.
As a result, the T-Bane metro was stopped in the area.
"An elk has fallen from a bridge over the track at Gjønnes station," Jan Rustad, communications officer with operating company Sporveien, told NRK.
"The elk was so badly hurt that we had to call wildlife authorities to come and put it down," Rustad added.
T-Bane services on Line 3 of the metro, on which Gjønnes is located, were closed as a result of the incident.
Rustad said to NRK that he did not know how for certain the elk had managed to fall from the bridge.
"Without knowing exactly, we guess that someone scared the elk such that it jumped over the gate at the bridge. When it falls from so high up it can easily break a leg," he said.
Elk also look for areas where less snow is on the ground during winter, which may help explain why the animal was on the bridge, he added.
In a similar incident on Sunday, an elk died from falling from a 12-metre high bridge in Hamar after being startled by people approaching it to take photos, NRK reports.