Barnsley crashed to a third successive defeat for the third time this season as they were dumped out of the FA Cup at the fourth round stage.
Barnsley have now been knocked out of the FA Cup by a side in a lower division to them in three of the past five seasons following defeat by Blackpool in 2016-2017 and Altrincham in 2015-2016.
This was the second time in three seasons that the Reds have conceded four in a FA Cup tie after being knocked out by a 4-1 defeat at Millwall in 2017-2018.
It is the first time they have conceded four goals in a FA Cup tie to a side in a lower league since 1964-1965 when fourth tier Chester won 5-2 at Oakwell when Barnsley were a third tier outfit.
There were six goals in a Barnsley FA Cup tie for the first time since last season's second round when they won 4-2 at Southend.
Cauley Woodrow had got Barnsley back into the game at 2-1, scoring his fourth FA Cup goal for the Reds.
Conor Chaplin netted a last minute consolation with his second FA Cup goal of the season, with him and Woodrow the last two Barnsley players to score in successive FA Cup games.
This was the fourth time both Woodrow and Chaplin have scored in a game this season (W1 D1 L2)
Barnsley scored at least twice yet failed to win for the eighth time this season (D4 L4), the most in a season since 2005-2006 (9 - D6 L3)
There were goals scored on 45+ and 90+ for the first time since February 2019 when Woodrow scored on 45 and Jacob Brown netted after 90+11 at Gillingham.
Remarkably there has been a 90+ minute goal scored in each of Barnsley's last four FA Cup matches.
Alex Mowatt came off the bench to feature, the first time he has played as a substitute since December 2018 in the Football League Trophy against Manchester City Under 21s.
There were no bookings in a Barnsley game for the first time in 22 matches - since a home game with Brentford in September. There have been 80 yellow cards shown in-between.
Barnsley were at least 2-0 down at half time in the FA Cup for the first time since the Quarter-Finals of the 2012-2013 season when they were 3-0 behind at Manchester City.
This was the second FA Cup meeting between Portsmouth and Barnsley, with the previous encounter occurring in the second round of 1906-1907 which Barnsley won 1-0 on their way to the Quarter-Finals.
At Fratton Park, Barnsley have now won just one of their last 21 visits, which came back in March 1999. They have failed to win any of their last seven visits, losing five.
This is only the second time since winning the FA Cup in 2008 that Portsmouth have reached the fifth round also doing so in 2009-10 .
Barnsley have now only reached the FA Cup fifth round twice in 21 seasons (2007-08 and 2012-13).
Barnsley have now lost 11 of their 16 away games this season in all competitions (W2 D3)
There were 15 on target shots in the game, the second highest total in a Barnsley match this season after the EFL Cup tie with Carlisle back in August (16)
There were only 16 fouls committed, the lowest in a Barnsley game since October against Swansea (13)
To compound matters Stoke defeated Swansea in the only Championship game of the weekend to extend the gap between Barnsley and safety to five points.
40. Brad Collins
2. Jordan Williams
6. Mads Andersen
7. Jacob Brown
9. Cauley Woodrow
16. Luke Thomas
17. Marcel Ritzmaier
18. Michael Sollbauer
22. Clark Oduor
24. Aapo Halme
27. Alex Mowatt (for Thomas 45)
4. Kenny Dougall (for Halme 69)
1. Samuel Radlinger, 3. Ben Williams, 14, Kilian Ludewig, 19. Patrick Schmidt, 20. Callum Styles.
35. Alex Bass
4. Tom Naylor
6. Christian Burgess
7. Ryan Williams
10. John Marquis
11. Ronan Curtis
13. James Bolton
14. Andy Cannon
20. Sean Raggett
33. Ben Close
42. Steve Seddon
19. Marcus Harness (for Williams 78)
26. Gareth Evans (for Cannon 90)
22. Ellis Harrison (for Marquis 90+2)
1. Craig MacGillivray, 9. Oliver Hawkins, 16. Jack Whatmough, 38. Brandon Haunstrup.
Portsmouth manager Kenny Jackett said:
“It was certainly an exciting game and I thought there would be opportunities at both ends of the pitch.
“I’m pleased to say we took more of the chances in what was quite an open contest, with some very good finishing.
“We couldn’t sit off Barnsley as the home side and we were always looking to take the game to the opposition.
“I think that it helped for Ronan to miss the Scunthorpe match on Tuesday night because he had a lot of energy, while Ben also looked lively and scored a good opening goal.
“We’re through to the fifth round now and ends a good week for us – we’re looking for our cup runs to continue.
“My thoughts now quickly turn to the league and facing Lincoln on Tuesday, then Sunderland next Saturday.
“But our supporters should be encouraged by the performance and hopefully we can have a really strong finish to the season.
“We’re guaranteed to have at least 59 games – and that’s without going any further in the cups or being in the play-offs.”
FA Cup Fourth Round results:
FRIDAY 24TH JANUARY 2020
Northampton Town 0-0 Derby County
Queens Park Rangers 1-2 Sheffield Wednesday
SATURDAY 25TH JANUARY 2020
Brentford 0-1 Leicester City
Burnley 1-2 Norwich City
Coventry City 0-0 Birmingham City
Millwall 0-2 Sheffield United
Newcastle United 0-0 Oxford United
Portsmouth 4-2 BARNSLEY
Reading 1-1 Cardiff City
Southampton 1-1 Tottenham Hotspur
Son Heung-Min 58
West Ham United 0-1 West Bromwich Albion
Hull City 1-2 Chelsea
SUNDAY 26TH JANUARY 2020
Manchester City 4-0 Fulham
Gundogan pen 8
Bernardo Silva 19
Tranmere 0-6 Manchester United
Greenwood pen 56
Shrewsbury Town 2-2 Liverpool
Love og 46
Cummings pen 65
MONDAY 27TH JANUARY 2020
AFC Bournemouth 1-2 Arsenal
Sky Bet Championship
SATURDAY 25TH JANUARY 2020
Stoke City (19th) 2-0 Swansea City (7th)
Barnsley lie in 22nd place in the Sky Bet Championship with 24 points from 29 games. We are 22 points outside the Play-Offs, 28 points outside the Automatic Promotion Places, 29 points outside First Place and 5 points inside the Relegation Zone.
Up to 26/1/20
On The Road:
Sky Bet Championship Matchday Thirty: Charlton Athletic v Barnsley, Saturday 1st February 2020. Kick-Off: 3pm
Sky Bet Championship Matchday Thirty One: Barnsley v Sheffield Wednesday, Saturday 8th February 2020. Kick-Off: 1:30pm