West Midlands Combined Authority (WMCA) bosses said the trial scheme – Thrive into Work – had been a success in helping residents.
The project, which launched in 2018, helps unemployed people who have mental or physical health conditions to get back into the workplace.
Now leaders have secured £1.1 million of Government cash to extend the project until July in a bid to help more people who are struggling.
West Midlands Mayor Andy Street said: "Getting 600 people back into work is an outstanding achievement, creating positive health, social and economic benefits allowing residents to thrive.
"The pandemic has had a damaging effect on employment but schemes like Thrive into Work show that the targeted, hard work being put in by the WMCA is contributing to a fairer, healthier West Midlands."
Father-of-two Matt Wagg is among those who have received help from the scheme after he left his job as a delivery driver due to osteoarthritis in his knees – which made it too painful to do the job.
The 47-year-old, from Oldbury, received six months of support which led him to a job as a school caretaker – tasked with keeping the school operating, including during the coronavirus outbreak.
He said: "I feel so much better compared to how I was before I enrolled on Thrive into Work, it provided me with someone to push me in the right direction and I’m like a different person to how I was then."
It comes as research from the Centre for Mental Health shows poor mental health is responsible for 72 million working days lost, costs around £34.9 billion each year, and is strongly associated with social and economic circumstances – such as people living in poverty.
Councillor Izzi Seccombe, WMCA's portfolio lead for health and wellbeing, said: "Thrive into Work is important because it can help citizens regain confidence, independence and a sense of purpose.
"I am delighted it’s previous success will be built upon, helping to support people in our region rebuild their lives and get back into the workplace."
To find out more about Thrive into Work visit wmca.org.uk/what-we-do/thrive/thrive-at-work/thrive-into-work