Michael Beaumont and Simon Scott were placed on travel insurance rather than work cover by Wilsons Security during their time at the centres.
It was only when both men were injured that they discovered they were not entitled to work cover and they claim the travel insurance company, Accident and Health Insurance, has refused to adequately cover them for their injuries.
Mr Beaumont sustained a shoulder injury when he broke up a fight between two asylum seekers during a meal break on Manus Island, something that he said was commonplace in the detention centre.
"I went for the aggressor and grabbed him and he broke loose straight away and so I went to grab him a second time, and I held in a restraint, sort of like a bear hug and he was sort of struggling violently to break free," he told 7.30.
"He was pretty strong, it felt like I was in a game of football again.
"I later found out that he had been in the weight room pumping up for a session before coming in for a fight and I was standing there cold so I got twisted back and forth."
Mr Scott's shoulder was badly injured when doing a training program in the early hours of the morning on Nauru when a local Nauruan guard charged at him.
Mr Scott, whose job at the security company was terminated last year after posing in a photo with Pauline Hanson during a Reclaim Australia Rally, is calling on the Federal Government to step in after he was told he needs surgery on his shoulder.
"The Immigration Department should conduct an investigation into how my injury has been handled for a start," he said.
"I'm an Australian worker, I have an Australian workplace agreement, I'm protected under those agreements and it's as simple as that, and I just haven't been... I have been cast off to the side," he said.
Guards 'issued with knives' to cut down asylum seekers
As part of their work, each guard was provided with a uniform, first-aid kit and a "cut down" knife.
Mr Beaumont said he was surprised when he was fist given the knife.
He was told it was designed specifically to cut down asylum seekers who tried to hang themselves.
"I just thought it was another piece of kit being issued and I was hoping it was a piece of equipment I wouldn't need to use," he said.
But Mr Beaumont said he was required to use it on a number of occasions during his time on Manus Island when asylum seekers attempted to hang themselves.
"We had a double one day, we had one guy did it and we were busy getting him down and making sure he was OK and the crowd was gathering around and the second did it," he said.
"The drill is, the guy goes in, grabs the person's body weight, hooks from behind, steps forward and cuts the thing down that they're hanging with and releases them."
Official figures from the Immigration Department say there were 55 cases of self harm on Manus from July 2014 to July last year, including men stitching their lips and hangings.
Fights were also common.
Maurice and Blackburn workplace injury lawyer Alison Barrett said Wilson had contractual obligations to look after their workers.
"In taking out the contract with the Australian Government or with Transfield, which they are directly contracting to... they have a duty of care with their workers and they need to meet the basic requirements of workers compensation insurance," she said.
"They can't blame-shift and they can't point the finger at someone else."
A Department of Immigration spokesman said the department did not have "oversight or access" to information regarding work cover claims.
"The department requires contracted service providers and their sub-contractors to have their own workers' compensation insurance arrangements," the spokesman said.
In a statement to 7.30, Wilson Security said it had comprehensive accident compensation policies for workplace injury.
"Wilson Security takes the safety of our employees extremely seriously and has an independently assured program in place throughout its operations," it said.
"Wilson Security is unable to make comment on any individual cases due to privacy, however can confirm adequate cover was provided to the individuals in question and deny that any wrong doing has occurred with regard to the assessment of these cases."
Simon Scott has engaged a lawyer to get compensation from Wilson Security for his injury.
Michael Beaumont is now taking Wilson Security to the Fair Work Commission.
"Yeah, I'm pretty angry at Wilsons, the way they treat people," Mr Beaumont said.
"I'm not real happy about it at all."