The Blues have landed the man they have targeted to bolster their left flank on a two-and-a-half year deal from Sunderland - with the club holding an option to extend his stay by another 12 months.
The 23-year-old becomes Pompey’s fourth January arrival and second deal of the day, following the signing of Crystal Palace keeper Ollie Webber.
Blues boss Danny Cowley told the official site: ‘Denver is a young player who wants to get better every day and he brings us some outstanding athleticism and energy.
‘He will add quality in the final third and we really like his wonderful ability to receive the ball on the back foot and play forwards.
‘We’re a forward-thinking team and the attributes he possesses are really aligned with our way of playing.
‘It’s great that he can play as a left wing-back or on the left of a back four because it gives us the flexibility we want in our squad.
‘He has all the attributes in his toolkit to be a really good defender and we’re looking forward to working with him.
‘Everyone we contacted spoke so well of Denver in terms of his professionalism and the way he conducts himself.
‘He was a breath of fresh air from the moment we started talking with him and you can see his ambition. He also loves football and for us, that’s really important.
‘I’m really excited about the business we’ve done this January and I believe we’ve made some real progress.’
A message from the Editor, Mark Waldron
Get 30 per cent off our sport subscription, which gives readers unlimited access to all our Pompey and grassroots coverage for just 9p a day, by using the promo code JanSports30. The deal expires at midnight on January 31.