As a 22-year-old central midfielder who played for Argentina at the Olympics this summer, Payero arrives with plenty of pedigree.
The deal was in the pipeline before he headed to Tokyo but it will be Friday before he is finally given permission to train with his new team-mates, who start their new Championship season at Fulham on Sunday.
“Martin will be a great addition to the squad," commented manager Warnock.
“I think he will be an exciting signing, we’re delighted to get everything done, and we’re looking forward to working with him.
“I know Martin is looking forward to it, and he can’t wait to play in front of our fans.”
Payero has played with Banfield and Talleres in his homeland and although he is yet to play for Argentina's first team - men's Olympic teams are under-23 sides - he has trained with them.