Wolves are chasing the centre-back, who is rated at £4million, as boss Mick McCarthy reshapes his squad ahead of the forthcoming season.
O'Hara played in the same England team as Mills at youth level and reckons the 24-year-old would be a good acquisition for Wolves.
"I played with him a few times for the England age group teams and I think he's a fantastic player," said O'Hara.
"He's a good lad and he'll fit right into our squad. It's important to fit in straight away with the boys, and he'll have no problems.
"He had a great season in the Championship with Reading and if we can get him then that would be great."