The Macedonian-born striker, who trained with the Highlanders on their summer tour in the Netherlands, has secured a six-month loan move from Swiss Superleague club Grasshopper Zurich.
Mustafi is a target who clearly excites County manager Derek Adams, who had been in the hunt for a frontman of power and presence.
The 23-year-old fits the bill, standing at 6ft 3ins and having a strong pedigree from top-flight spells with Grasshoppers and FC Basel.
Adams said: “Orhan has good ability and good knowledge of the game. He takes the ball in to feet and he’s strong.
“He’s 6ft 3 ins, good in the air – but also a very good finisher. And he’s only 23.”
The newcomer, who still has a year to run on his Grasshoppers contract, is now in contention for Saturday’s curtain-raiser against Celtic in Glasgow.