The report found more than half (54%) will work while on annual leave, 71% felt more worried in the run up to holiday than in previous years, and 17% will return from holidays more stressed than when they left.
In the study of 1,200 UK managers in June, the majority said they will be reading and responding to emails and nearly a third (31%) said they would be taking phone calls.
Charles Elvin, chief executive of the ILM, said the study paints a picture of an over-stressed workforce.
"It is particularly worrying to see that such a large proportion of managers approach their holidays with a sense of trepidation and feel compelled to work when on annual leave," Elvin said.
"Stress can take its toll, not only on individuals' wellbeing, but also on the productivity of the wider team and organisation. It is so important that people are able to make the most of their time off work to fully relax, reflect and unwind, so they can return to the office with renewed energy, fresh ideas and perspective.
"Organisations can increase positivity and performance by encouraging staff to plan for their leave, hand over their responsibilities, and ensure they switch off and recharge both themselves and their Blackberries."
The survey found that holidays are a time when people start to re-think their career paths. Almost a third of managers (30%) had thought about changing or leaving their job while on holiday and of those 38% had moved jobs as a result.
