The Delfland Institute of Mental Health study of 545 men found the most optimistic were about half as likely to die from cardiovascular disease.
Researchers thought it was likely to be because optimists exercised more and were better at coping with adversity, the Archives of Internal Medicine said.
Heart experts agreed being positive could have a significant effect.
Previous research has shown optimists tend to live longer but this is the first to find a specific link to better heart disease rates.
This new study adds weight to the argument that if we feel optimistic and supported it may have a positive effect on our health and hearts
The men who took part in the latest study, who were between 64 and 84 and were followed for up to 15 years, were asked to fill in a questionnaire to determine whether they were optimists.
Researchers found that those classed as optimists in 1985 were 55% less likely to die of heart disease or stroke by 2000 when taking major factors such as smoking and family history into account.
Lead researcher Erik Giltay said: "It's likely that optimism affects cardiovascular health in a number of ways, both directly and indirectly."
He said it was not necessarily to do with lower rates of depression.
"One possibility is that optimists are better at coping with adversity, and may, for example take better care of themselves when they do fall ill."
Exercise
And he added optimists were more likely to exercise and an individual's disposition could affect health through its influence on the nervous, immune and hormonal systems.
But he said pessimists need not be resigned to having heart and stroke problems as they could reduce their risk through other measures such as becoming more active and smoking less.
Alison Shaw, cardiac nurse at the British Heart Foundation, said: "This study suggests that being positive and optimistic as we get older may have some effect on our wellbeing and reduce the risk of heart and circulatory disease.
"Previous research on lack of social support, depression, and having lack of control in life showed that people may be more at risk of developing coronary heart disease.
"This new study adds weight to the argument that if we feel optimistic and supported it may have a positive effect on our health and hearts."
