Morgan Trowland and Marcus Decker began climbing the bridge stanchions in the early hours of 17 October last year.
The men then eventually climbed to about 200ft above the water and remained suspended over the carriageways. Their actions led to the bridge being closed for 41 hours.
They stated their actions were in protest, but those actions caused disruption to hundreds of thousands of people on the M25 and surrounding roads, many of whom lost out on salary, missed significant family occasions or could not access medical help when it was urgently needed.
Both men were removed from the bridge by specially trained officers on the afternoon of 18 October.
Officers had trained on a specialist-raised platform at a nearby fire station before it was brought to the bridge.
Once they were safe, both men were arrested on suspicion of causing a public nuisance and subsequently charged.
They denied the charges but were found guilty of the offence at Southend Crown Court.
They appeared at the same court today, Friday 21 April, to be sentenced.
Trowland, 40, of Drummond Way, Islington, and Decker, 34, of no fixed address, were sentenced to three years and two years and seven months respectively.
