Footage shows the Islington MP walking past rows of empty seats in the clip before sitting on the ground between carriages for a video blasting conditions faced by Britain’s commuters.
The remarkable clip, released by Virgin Trains, comes after Mr Corbyn was praised for reportedly rejecting the offer of a first class ticket and opting to sit on the floor.
Virgin Trains confirmed the CCTV footage showed Mr Corbyn and his team walking past available seating before starting filming.
The train operator said the crew helped him to a coach where seats were available and that he sat down for the rest of his journey.
The Labour leader, who was filming for a Guardian video, was travelling to Gateshead for a hustings event with leadership challenger Owen Smith.
In the video, Mr Corbyn said: “This is a problem that many passengers face every day on the trains, commuters and long-distance travellers.