Sahilal Sabaratnam and Thiruthanikan Thanigasalam had pleaded guilty last year to providing material support to terrorists.
Both were sentenced to 25 years behind bars on Monday in federal court in Brooklyn. Two other co-defendants were sentenced last week.
The FBI lured the four men from Canada in 2006 to a meeting in New York with undercover agents posing as arms dealers. They were arrested after allegedly agreeing to a shipment of 10 surface-to-air missiles and 500 AK-47s.
Government forces routed the Tamil insurgency last year to end more than 25 years of civil war.