The Sydneysider and Vietnam veteran, 65, has spent decades in the grip of post-traumatic stress disorder and depression triggered by his time in the navy.

But in March, after a series of knockbacks, Mr Uyeda won his 15-year legal battle for a veterans' disability pension.

"Just to be told they believe me at last, it's taken about 30 years off me in age the way I feel," Mr Uyeda said.

"It's been a hard battle but that's life. I try not to hold any regrets about it."

Mr Uyeda said he was a "naive kid" from Revesby in Sydney's south-west when he joined the navy at "17??".

What he saw in Vietnam and in Darwin during the Cyclone Tracy clean-up in December 1974 and early 1975 would have a profound effect on his life.

"Every time I heard someone was hurt I'd have to hide somewhere and start bawling; I didn't know why," Mr Uyeda said.

"These things just kept creeping up on me."

For years he thought he was "the only one" and a "weak link" - until he reconnected with former colleagues who felt the same.

Mr Uyeda first applied for a Commonwealth veterans' disability pension in about 2002 but was turned down that year, and again in about 2006.

"At the time I got knocked back I just felt I didn't deserve anything," he said.

He already felt "rejected after coming back from Vietnam with the reception we got" from the community and has "never marched" on Anzac Day or worn his medals.

He was ready to give up when his brother-in-law put him in touch with Legal Aid's Veterans' Advocacy Service.

On March 31, the Veterans' Review Board told Mr Uyeda it had overturned a Repatriation Commission ruling last year refusing him a pension on the grounds his PTSD and depression were "not related to service".

The review board ruled his medical conditions were "defence-caused".

"lt's a big load off me," Mr Uyeda said.

"I can't thank Legal Aid enough for what they've done for me in such a short time."

Esther Rice, a lawyer from the Legal Aid NSW Veterans' Advocacy Service, said "some veterans are reluctant to claim their entitlements, while others may have tried in the past and found the process overwhelming".

"Ensuring that our veterans have access to the compensation they are entitled to is one small way the community can recognise their service," she said.

"Our specialist advocates at Legal Aid NSW have tremendous experience in helping veterans and their loved ones to understand their rights, and to tell their stories in a way they can really be heard."

Mr Uyeda said he was going on a motorcycle ride with Vietnam veterans on Anzac Day.

"It's on those days you can let your guard down," he said.

He wanted young veterans to be aware of their rights and make an "early start" seeking help for mental illness and claiming hard-won entitlements.