N’Djamena, which is situated less than 100 kilometres from the Nigerian border, was hit by a series of suicide bombings in June and July, 2015.
The militants were convicted over their roles in twin attacks on the capital in June, which killed at least 38.
According to chief prosecutor, Bruno Mahouli Louapambe, the men were found guilty of charges including criminal conspiracy, killings, wilful destruction with explosives, fraud, illegal possessions of arms and ammunition, and using psychotropic substances.
A judicial source revealed that the trial had been due to last eight days, but it was speeded up and moved on Thursday to an undisclosed secret location.
Among those convicted was Mahamat Mustapha, aka Bana Fanaye, the man described as the “mastermind” of the attack by Chad’s Interior Minister Abderahim Bireme Hamid.
It would be recalled that shortly after the attacks, the government of Chad reintroduced the death penalty for acts of terror. However, opposition and civil liberties groups have spoken against the new anti-terror legislation, noting that it could be used to curb civil rights.
Chad also banned people from wearing the full-face veil as part of efforts to prevent terrorists acts.
Last month, Chadian military recorded more successes in the war against the deadly Boko Haram sect. The army spokesperson revealed that the country’s security forces slaughtered 117 militants in the last two weeks.