The RSL wants the government to set up a dedicated centre to safeguard returned soldiers' health amid reports that more than 40 veterans have taken their own lives this year.
The NewsCorp Australia report on Sunday found 41 diggers have so far committed suicide in 2016, which is equal to the number of Australians killed in 13 years of combat in Afghanistan.
The investigation suggests that Aussie soldiers have returned to civilian life with depression, anxiety issues and post traumatic stress disorder, but have struggled to find assistance.
RSL national president Rod White said a united effort was needed look after the mental health and wellbeing of current and ex-serving troops.
The RSL wants a "through-life" care model for former soldiers, including the re-establishment of a permanent Centre for Military and Veteran Health.
"We must not, cannot lose any more veterans to suicide," White said.
"Our veterans and their families deserve the very best support available and it's time the government coordinated a united approach to give them that.
"Frustratingly, we don't even know the size of this terrible tragedy -- there is no register of service and ex-service suicides."
He urged veterans to reach out for help from the RSL's national network but said the government needed to step up its support.
Soldiers especially needed help before they moved out of active service, he said.
"What is needed now from government is a proactive and collective focus on providing emotional and physical support to defence personnel well before they transition out of service and run the risk of feeling isolated or disenfranchised."