The research from TotalJobs found that a quarter of employees in the South East are considering quitting their jobs due to loneliness.
Half admitted to feeling lonely at work, but a third of those surveyed admitted that they did not confide in anyone about their mental health.
Pressure and not fitting in with work colleagues were found to be among the leading causes of loneliness at work.
Half of employees said their employees were not doing enough to combat loneliness.
A spokesman from TotalJobs said: “These findings should highlight a cause for concern for colleagues and employers alike, as the issue is having a detrimental impact on workers’ mental health and wellbeing in the workplace, a place in which many spend most of their time.
“It is evident that workplace loneliness still carries a stigma and more needs to be done to encourage workers to have open conversations about loneliness in their places of work.
“We would strongly encourage men and women, millennials and boomers, to confide in someone about their loneliness, whether inside or outside of work.
“Talking to someone can help you to feel less lonely.
“Equally, we would urge employers to be proactive in putting measures in place so those suffering with loneliness in the workplace, have a network of people and tools to support them.”
Emma Mamo, Head of Workplace Wellbeing at Mind said: “Staying silent is one of the worst things people in difficulty can do.
“Opening up to a colleague about how they’re feeling can help them feel more relaxed about chatting to a manager.
“Even if they don’t want to speak about it then, you’ve let them know you care and will be there for them when the time is right.”