Northern Ireland fans spokesperson Gary McAllister says Michael O'Neill's appointment as Blackburn Rovers manager "hasn't been very well received" by supporters.
O'Neill will take joint-charge of Championship side Blackburn and Northern Ireland until the end of the season after a short-term deal was agreed.
Blackburn are currently in the relegation places, while Northern Ireland face a World Cup play-off semi-final in Italy on 26 March as they look to reach the finals for the first time in 40 years.
McAllister, who is the chair of of the Amalgamation of Official Northern Ireland Supporters' Clubs, said O'Neill's appointment at Ewood Park came as "something of a surprise".
"Over the last couple of days there has been some speculation, but it quickly grew legs and now there has been an announcement.
"When you look at the reaction online from fans, I don't think it has gone down particularly well. I think you have to be honest."
McAllister said he would rather focus on the Italy game in Bergamo, rather than O'Neill's future as Northern Ireland manager, but did say the "timing was far from ideal" with just six weeks until the play-off.
"I'm not surprised by the reaction we have seen from fans, and the timing is far from ideal," he added.
"I want us all to focus on the Italy game, it will be a massive challenge for us but it's a real opportunity to get to the World Cup for the first time in 40 years.
"But looking at the reaction of fans, it has not been well received unfortunately."
When asked if the atmosphere would be impacted for the game in Italy, McAllister said he did not think it would make a difference.
"Northern Ireland fans are very loyal to our team. We'll be travelling in numbers," he said.
"We'll be united behind our team, as we always are.
"Whoever the manager of our team was in the past, future or even today, we are always 100% behind the team."