The Australian government says it will investigate the footage.
The video comes four years after Australia had to suspend cattle exports to Indonesia because of mistreatment.
Animal rights activists say the footage shows cows having their skulls smashed by sledgehammers at an abattoir in Vietnam.
Australian Prime Minister Tony Abbott said on Wednesday that the government would probe the incident, but not suspend live cattle exports to Vietnam.
Although not released yet due to its graphic nature, the video has caused the Animals Australia rights group to file a complaint with the agriculture department in Canberra.
Meanwhile, Australia's Royal Society for the Prevention of Cruelty to Animals has called on the government to halt the live cattle trade with Vietnam.
Sales of Australian cattle to Vietnam increased more than 700% between 2008 and 2014, and will be worth A$117m ($92m, Â£60m) in the upcoming season starting in July.
Animals Australia has tweeted about the situation in Vietnam, urging people to demand their MPs ban the export of live cattle using the hashtag #BanLiveExport.
The group plans to stage a rally against live cattle trade on Saturday at Adelaide's Parliament House.
Animal rights activists say they have obtained video showing exported Australian cattle being killed with sledgehammers in Vietnam.