This has been agreed between the two clubs so that the loan will run until the final Saturday of the Football League season on May 4th.
Birmingham do, however, have the option of recalling Woodhouse anytime after the first month of the loan deal.
Ronnie Moore, obviously delighted with the capture of a premiership player, said: "It looked at one time as if the deal would fall through with so many clubs after Curtis.
"But the big thing was he said he wanted to come to Rotherham. He has taken a big drop in wages and that is a magnificent gesture.
"That is a rarity and it's nice we have someone who just wants to come and play football, not sit in the comfort zone.
"He is a very tenacious player who likes to close opponents down. He plays the easy ball, gets in the box and will bring a lot to us," he told the club's official website.
Curtis Woodhouse Statistics