Work pressures during the recession have caused a big rise in mental health problems, the charity says.
A survey for Mind suggests that one in eleven British workers have been to the GP for stress and anxiety from the financial squeeze.
Seven percent said they were prescribed medicines to help them cope.
The Confederation of British Industry said employers were improving at caring for workers' mental health, but it was important to increase understanding.
The last couple of years have been an anxious time, even for those who have not found themselves out of work.
Many have had overtime cut, worked longer hours, or worried about job security.
It felt like there was a big black cloud over me
For some people, the pressure it causes can feel uncontrollable, and MIND believes mental health issues will soon become the biggest cause of work-related absence.
Their survey of 2,050 workers found that about a third were working harder and nearly half worried about the security of their jobs because of the recession.
Nine per cent had been to their GP as a direct result of pressure related to the financial squeeze, and 7% were prescribed medicines like anti-depressants to help them cope.
One in five said work stress had made them physically ill, and one in four had been reduced to tears at work because of unmanageable pressure.
Carlene Brown found herself under pressure to work hours of overtime every week in her sales job in Birmingham.
She found herself struggling to cope and slipping more and more deeply into depression.
"It felt like there was a big black cloud over me," she said.
Her company was unsympathetic when she took time off, and eventually made her redundant.
"It was such a relief," she said, "I don't think you ever get over depression, and I felt very bitter, but I have learned to live with it."
Mind is calling on companies to improve the atmosphere in workplaces and show more understanding about mental health problems.
"Working conditions have been incredibly tough for the last couple of years, " said Mind's chief executive, Paul Farmer.
"It's more important than ever that businesses look at how they can manage stress levels and improve the working environment for all their employees."
BT's indoor garden is designed to soothe staff
Some companies have cut back on the support they offer workers because of the financial squeeze, but British Telecom has taken the opposite approach.
More employees than ever have been using its counselling service, and it has been improving back-up for stressed workers.
"Mental health is one of the biggest issues for us," said Paul Litchfield, the company's chief medical officer.
"People in good mental health are productive and engaged. It makes good sense to support people's mental and physical health."
As well as more conventional support, BT has introduced an indoor vegetable garden to help improve the atmosphere at work.
It is the kind of innovation MIND wants to see in other companies.
"It doesn't have to be costly," said Paul Farmer, "and it can really improve the morale of a workplace. There's a strong business case to take these measures."
The CBI said companies take mental health seriously and have already improved workers' support.
Neil Carberry, head of employment policy, said: "The key thing is developing understanding among fellow employees and line managers on the issues."