Yep, Stipe Miocic has seen that footage of Daniel Cormier training with Steven Seagal back in the day ... but he ain't worried about it!
The footage was shot back in 2015 when Cormier was getting ready to fight Jon Jones at UFC 182.
Seagal -- who considers himself a martial arts expert -- hit it off with Cormier and offered to share some of his secret fight moves ... but only if UFC turned off the cameras.
Cormier and UFC obliged, and now -- in theory -- he's been trained up in the ways of the guy from "Under Siege.