The Sunderland academy graduate is heading to the south coast for a medical and to complete the formalities of the move.
It's understood that the move will land Sunderland in the region of £200,000.
A significant sell-on clause will also be included in the deal, protecting the Black Cats should the 23-year-old make rapid strides in Danny Cowley's side.
Hume has long been rated highly behind the scenes at Sunderland, but injuries checked his impressive development during Phil Parkinson's tenure.
Injuries and a protracted contract saga over the summer left him behind on match fitness during the current campaign and Dennis Cirkin has recently established himself as the club's first-choice centre back.
Lee Johnson confirmed last week that Hume had been frustrated with his game time of late and it's understood that all parties felt a fresh start would be the best outcome.
Cowley has been tracking Hume since the summer, and believes he is tailor-made to slot into his current system at wing-back, where is lacking a natural option.
Both the Sunderland and Portsmouth managers confirmed talks were ongoing at the weekend.
"There is interest from Portsmouth," Johnson said on Saturday night.
"Nothing has been agreed yet but I believe there have been verbal offers.
"I took the decision to leave Denver out, because I felt it was fair on him. If he comes on and scores the winner, it could become difficult for him.
"If Danny Cowley asks for him for our team, it's difficult.
"He had the day off yesterday and I just felt it was the right thing to do.
"But if it goes past this week and nothing gets done, then he will absolutely be part of our squad moving forward."
Cowley added: "He’s a player we would like to bring in. We’d like an attacking left-back and he’s one of two we’ve inquired about.
"I believe we’ve made an offer, but I’ve been focusing on this game and don’t know any more than that at the moment."
Sunderland beat Portsmouth at the Stadium of Light on Saturday to bolster their automatic promotion hopes.
They travel to Bolton Wanderers on Saturday.