Chowdhury Mueen Uddin, who lives in Britain, and Ashrafuzzaman Khan, who lives in New York, were found guilty by a three-judge panel of abducting and murdering 18 people in December 1971, including nine university teachers, six journalists and three physicians.
The two were tried in absentia after they refused to return to Bangladesh to face trial.
Bangladesh says Pakistani soldiers and local collaborators killed 3 million people and raped 200,000 women during the 1971 war.
The two men were members of Jamaat-e-Islami during the war. The Islamic party is an ally of the country's main opposition Bangladesh Nationalist Party, headed by former Prime Minister Khaleda Zia, a rival of current Prime Minister Sheikh Hasina.
Hasina formed the special tribunal in 2010 to try war crimes suspects.
A Supreme Court ruling last month that upheld the conviction and death sentence of a senior member of Jamaat-e-Islami, Abdul Quader Mollah, triggered deadly clashes and a nationwide general strike.