Figures from the UK Annual Leave Survey, compiled from questions sent to over 2,000 people, also suggest that only 50% of people take all of the holiday they are entitled to.
Almost half (44%) of employees admit to working while they are on leave. The Scottish are the most likely to do this, with 57% saying they work while away. Welsh people do the least work while on holiday, with only 25% reporting that they carry on with work tasks.
Nearly one in five (19%) respondents said they have trouble switching off from work on holiday. This rises to 25% for people aged 25- to 34-years old, who have the hardest time mentally distancing themselves from the workplace.
A similar number (18%) have been contacted by a colleague about a work matter while on holiday, and 13% have been contacted directly by their manager.
Joe Wiggins, senior PR manager and spokesman for Glassdoor, told HR magazine the findings were "worrying" for UK employers.
"If I were a senior HR professional these figures would certainly give me pause for thought," he said. "Employers should be encouraging their staff to take all of their holiday, recharge their batteries and come back to work refreshed."
Wiggins added that working on holiday is becoming more common, and "the lines between home and work life are increasingly blurred".
"With a culture of 24/7 communication, it's inevitable people will be taking work home and away with them," he said.