The left-back has completed the formalities of his permanent move to AFC Wimbledon on a free transfer and signed a two-and-a-half-year deal at Plough Lane.
He’ll be available for the Dons’ home game against Shrewsbury on Saturday and represents manager Mark Robinson’s third signing of the January transfer window.
Brown is the seventh senior player to leave Fratton Park this month, following Ellis Harrison, Paul Downing, John Marquis, Gassan Ahadme, Miguel Azeez and Alex Bass (loan) through the exit.
'I don't think I realised how much it would mean': ex-Cardiff City and Bristol City man's Portsmouth admission as he chases winning Fratton feeling after homecoming
Former Portsmouth, Sunderland and Millwall ace Aiden O'Brien suffers setback as frustrating start to life at Shrewsbury continues
Danny Cowley makes Portsmouth team selection admission following Cheltenham win - and gives honest assessment of current squad amid early-season promotion hopes
The role ex-Leicester City, Birmingham City and Charlton Athletic man wants to maintain at Portsmouth after guiding city's young gems at Reading
Colby Bishop gives Spurs loanee and England youngster Dane Scarlett raving reviews after making Portsmouth league debut
Former Sunderland defender Hume is seen as Brown’s long-term successor at PO4, having moved from the Black Cats for a fee in the region of £200,000 this week.
The 31-year-old spent three-and-a-half years at Pompey following his move on a free transfer from Bristol Rovers in 2018.
He made 131 appearances for the Blues, scoring six times.
Brown’s last outing for the club came against new employers Wimbledon on January 18 – a game that finished goalless.
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.