His family said Struck, a plain-spoken politician who was a leading lawmaker for Germany's center-left Social Democrats for almost three decades, died in a Berlin hospital.
Struck served as Germany's defense minister from 2002 to 2005.While an opponent of the Iraq war, he oversaw the early years of Germany's military engagement in Afghanistan, famously announcing that "German security is being defended in the Hindu Kush" mountains.
Chancellor Angela Merkel said in a statement that "Peter Struck's death fills me with great sorrow."
Merkel, who originally came to power in a so-called grand coalition with Struck's party in 2005, called him "a great parliamentarian" who strongly defended his positions but was always a reliable partner.
"With his death Germany is losing a steadfast and authentic personality, who embodied like almost no one else the country's defense policy," said Defense Minister Thomas de Maiziere.
"He liked the soldiers and they liked him," he added.
Since 2010 Struck had led the Friedrich-Ebert-Stiftung, a major foundation affiliated with his party.
A colorful personality, Struck was often pictured smoking a long-stemmed pipe, and had a penchant for riding his motorcycle boasting in a 2011 interview that he'd put 65,000 kilometers (more than 40,000 miles) on it over three years.
He was a lawmaker from 1980 to 2009, serving the Social Democrats for many years as chief parliamentary whip and caucus leader.
Struck is survived by his wife Barbara, three children and several grandchildren.