One in 10 people believe their work is "horrible", with many more saying it caused them to suffer stress, a new study shows.
A survey of 2,000 workers found that more than a third were negative about their work, with one in seven associating their job with being unhappy.
The report, published on the United Nations International Day of Happiness, said women were more likely to be anxious about work than men.
Business consultants Lee Hecht Harrison Penna said its research suggested that workers in London were the happiest in the country, while the least happy were in the South West.
Chief executive Nick Goldberg said: "With our working life and private life becoming increasingly integrated, negativity and unhappiness at work can easily spill over and become all consuming.
"While it is encouraging to see that 38% of employees have only positive things to say about work, our research also shows that more needs to be done by both the employee and employer to improve workplace happiness.
"Today marks a good day for employees to ask themselves if they are truly happy at work, and if not ask themselves why, and what steps they can take to address it."
One in five of those questioned said their work caused them stress.