The cash will go to the NHS Op Courage, a mental health service with a team of care coordinators – which has received 16,000 referrals since it launched in March.
Around 38,000 current and former members of the Armed Forces are thought to suffer from alcohol and substance misuse.
Defence Secretary Ben Wallace said: “We are forever indebted to the heroics and sacrifice of our service personnel, and pledge to ensure they receive support they need.”
Minister for Defence People and Veterans Leo Docherty said: “This support increase will help veterans who may be struggling. I urge any veteran to access this specialist support.”