Legendary actor James Caan died from a combination of serious heart problems ... according to his death certificate.
The document, obtained by TMZ, says James died from a heart attack and coronary artery disease -- the most common heart disease in the U.S.
The certificate says James also suffered from chronic obstructive pulmonary disease, also known as COPD, and congestive heart failure.
As we reported ... James died July 6 at 82 years old, but details were scarce aside from a family statement.