He was in charge of Wales from 2004-2010 and will face an emotional clash with his compatriots in the 2014 World Cup qualifiers.
"Toshack will arrive in Macedonia on August 25 and will be officially promoted the next day," FFM president Haralampie Hadziristeski told the body's website after meeting with the 62-year old in Barcelona.
"His debut will be away to Russia in a Euro 2012 qualifier on September 2 and we are also looking forward to his first home game against Andorra four days later," he said.
Macedonia are fifth in Group B with four points from six games and only a mathematical chance of qualifying for their first major tournament as an independent nation.
Toshack, set to take over from Mirsad Jonuz who was sacked in June after a string of poor results, was quoted as telling the FFM official website he was looking forward to the challenge of turning round Macedonia's fortunes.
"I am truly grateful that the FFM chose me to be the manager of the national team," he said.
"The people were great, open and gave me belief that we can work together to reach new heights for Macedonian football.
"I will watch the upcoming friendly against Azerbaijan and together with information about the Euro 2012 qualifiers Macedonia have already played, I will get a clear picture regarding the team's potential."
Toshack won three league titles, one European Cup and two UEFA Cups with Liverpool in the 1970s as a player and then managed several Spanish clubs, including Real Madrid during two brief spells with the nine-time European Cup winners.
Apart from Macedonia and Wales, Europe's 2014 World Cup qualifying Group A includes Croatia, Serbia, Belgium and Scotland.
"It will be hard to play against my Wales but I can't think how Welsh fans will react because I am a professional and will do my best to turn things around in Macedonia," he said.
"It is a tough group but it's also balanced."
