The 59-year-old has joined the former Blues boss’ backroom staff at Portman Road, following the announcement of his Fratton Park exit last week.
The duo previously worked together at PO4, with Keeley part of the coaching set-up Cook had at his disposal during Pompey’s 2016-17 League Two title-winning season.
Keeley, who enjoyed two spells at the Blues, departed the south coast as part of new head coach Danny Cowley’s first-team overhaul – a process that has already seen the Pompey boss bring in trusted recruitment analysts Matt Page and Toby Ellis.
He was joined by Joe Gallen and Jake Wigley in being let go by Pompey, as the ongoing revamp focuses not only on the playing squad but also the coaching set-up.
Speaking to the official Ipswich website, the former Brighton keeper said he had a ‘great feeling’ about being reunited with Cook.
Keeley said: ‘I can’t wait to get going. I’ve been in the game a long time but I still get a buzz about being involved in something good and I’ve got a great feeling about this.
‘I was at Portsmouth with Paul and I loved working with him. I was very close to going to Wigan with him when he left.
‘We have stayed in touch over the years and that shows you how we get on and I was delighted when he asked me to come to Ipswich.
‘He’s a proper football manager. He loves the game, he loves to see his teams playing attacking football and Ipswich is a massive club.
‘Like I said, I’ve just got a good feeling we are going to achieve something here. It’s a really exciting opportunity.’