The video posted on social media today, said the eight men were beheaded in the central Syrian province of Hama.
The men, wearing orange uniforms with their hands tied behind their backs, were led forward in a field by teenage boys.
They were then handed over to a group of IS fighters with each fighter receiving a knife from one of the boys before beheading the men.
An Islamic State fighter speaks in the video, using a derogatory term for Shiites and calling them "impure infidels."