ABC executives have told the high-wire walker he must wear the safety device out of consideration for viewers who tune in to the network's three-hour TV special on 15 June.
Unhappy Wallenda says, "I'm upset. I'm not used to it. I've never worn a tether before so it's just something else I have to contend with when I'm out there."
Wallenda, who was given special permission to become the first person to walk from Canada to America over the famous Falls, is a seventh generation member of the famous daredevil family the Great Wallendas.
Ironically, his grandfather Karl Wallenda's death was televised as he fell from the wire during a promotional walk in San Juan, Puerto Rico in 1978 - the year before Nik was born.
Nik returned to Puerto Rico last summer (11) to complete the walk between two high-rise hotels with his mother, Delilah.