The Slovenian was fired shortly after today’s 2-1 home loss to Wolves, the sixth and final game of his tenure, which failed to yield a victory.
It ended his reign in charge at 32 days, with his predecessor David Hockaday lasting 70 days.
Redfearn, who has taken charge of United on a caretaker basis on three previous occasions, took ten points out of 12 from his four games at the helm in a temporary capacity following Hockaday’s axing.
Redfearn presided over Leeds’ last win back on September 20, a 3-0 derby victory over Huddersfield.
On the decision to sack former Sturm Graz head coach Milanic, Cellino said: “I have given the order to fire him.
“I made a mistake with this guy. He is negative, he has a losing mentality. He has three points from six games, that is relegation (form).
“Neil Redfearn will take training on Monday. He is the new head coach, 100 per cent.”
Milanic had earlier accepted the frustrations of supporters who were calling for Redfearn to be appointed during long periods of the second half.
“I understand football, and I can understand this situation, when a new head coach has only a few points from six games, I can understand that,” Milanic said. “I am disappointed because we deserve some more points, This is not a good position for me and the team, but I still see good things that we make. I believe it (he can get it right).
“My job is to do this better, to improve. I am sure this one second half is not the work of one month. I work with my team a lot and it’s a young team without a lot of experience. We played a good first half, had chances, we had one goal. Then we began to play backwards.”