The new brigade will answer to the government of Iraq's autonomous Kurdish region, whose peshmerga fighters are playing a leading role in the war against the jihadists.
Fighters paraded and jumped through fiery rings in front of Kurdish and Assyrian officials in the northwestern town of Fishkhabur, near the borders with Syria and Turkey.
Most of Iraq's Christians lived in the Nineveh plain, an area between the main IS hub of Mosul and the Kurdish capital of Arbil, before IS fighters swept in seven months ago.
"Around 600 peshmerga from our Christian brothers in the Nineveh plain joined this course, which focused on physical training, military lectures and shooting exercises," said Abu Bakr Ismail, the commander of the training academy.
"All the participants are volunteers... and want to liberate their land from IS and then protect it," the Kurdish special forces major general said.
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The new brigade is called the "Tiger Guards" and was formed out of the remnants of an Assyrian force first created in 2004 to protect churches in the region.
Up to 100,000 Christians fled their homes overnight in early August when IS fighters who had already conquered large parts of Iraq thrust into areas controled by the peshmerga.
The exodus has been described as the worst disaster to befall the minority, which is one of the world's oldest Christian communities.
Iraq's Christians have not traditionally had strong home-grown militias and adopted a low profile when sectarian violence flared across the country a decade ago.
But those who haven't already fled the country have in recent months shown a willingness to take up arms and take their future into their own hands.
Several other Christian groups have formed in recent months in northern Iraq. They do not fall under the peshmerga's command but are hosted and supported by Kurdistan.