The outbreak in Edinburgh has already claimed the life of a 56-year-old man and there have been 41 confirmed cases and 48 suspected cases so far, the local health authority said.
Ten people remain in a critical condition in intensive care.
The latest death, at Edinburgh Royal Infirmary, was reportedly a man in his 40s. Health officials said he had significant pre-existing health problems.
Scotland's health minister Nicola Sturgeon said the number of cases was unlikely to rise.
"Despite this sad and tragic development, it remains the case that we believe the outbreak to have peaked. However, we continue to monitor the situation carefully," she said.
Britain's Health and Safety Executive and Edinburgh City Council are still investigating the source of the outbreak, with their probe so far focusing on industrial cooling towers in the southwest of the city.
Improvement notices have been issued to two firms, a distillery and a pharmaceutical company, about the cooling towers, although authorities have said they are not necessarily the source.
Legionnaires' disease is contracted through the inhalation of contaminated water droplets and is not known to be transmitted from person to person.