A 1-1 draw with the league leaders extended Barnsley's winless run in all competitions to three matches, their worst run since April (four)
They are winless in four league outings which is their worst run at this level since losing seven in a row between October and November 2015.
After winning five out of six matches in all competitions (excluding shootouts) they have won only one of the subsequent six.
This result also saw Barnsley drop to seventh in the table - the first time this season they have been outside the top six.
Gareth Evans gave Portsmouth the lead, only the second time the Reds have conceded the opening league goal at Oakwell this season - however both have come in the last two home outings.
Just as in that previous game - against Doncaster - Cauley Woodrow netted a second half equaliser, his sixth goal in his last eight appearances in all competitions - the exact same record Oli McBurnie had in his first eight appearances for Barnsley last season.
The Reds remain unbeaten when Woodrow has netted (W3 D2)
Brad Potts set up Woodrow's goal with the on loan Fulham man sliding in his right wing cross. It was Potts' fourth assist of the season and his first since the 4-0 FA Cup win over Notts County.
Evans opener came in the 43rd minute and was the first time Barnsley have been behind at half time at Oakwell in any competition since March 17th against Millwall (17 home games ago)
This was only the second time in six visits to Oakwell that Portsmouth have managed to score.
Pompey scored with one of only two shots in target - in the last five matches Adam Davies has faced 16 on target efforts and conceded 11 goals.
This was the 11th time this season Barnsley have conceded the first goal (all comps) and only the sixth occasion they have managed to avoid defeat (W3 D3)
This result kept both Barnsley unbeaten at home this season (10 league games) and Portsmouth unbeaten on the road (11 away league games)
These records give Portsmouth the best away record in the division and they have conceded the least in League One on the road (8) however with this being Barnsley's fifth home draw they have only the eighth best home record yet have conceded the least amount of home goals (7)
Of the five home draws Barnsley have had this season, four of them have finished 1-1 with the exception being a 0-0 against AFC Wimbledon.
It is Barnsley's best home start to a season since 2003-2004 (12 matches) and means Daniel Stendel is the first Barnsley manager to go unbeaten in his first 10 home league games since Gudjon Thordarson in that 03-04 campaign (two out of three of Barnsley's foreign managers have now accomplished this)
It is comfortably Portsmouth's best away start to a season - prior to this their best start was six unbeaten away matches.
Overall, excluding a penalty shootout Barnsley are unbeaten in their first 14 home matches - the best start since 1967-1968 when they went the entire season without losing at Oakwell - all in the league.
Including last season the Reds are now unbeaten at Oakwell for 18 matches (all comps), W9 D9 their best home run since 2005-2006 when they went 19 without defeat in front of their own supporters.
Barnsley had a total of 18 shots in the game - the most since Plymouth at home on the 2nd October (19) - this also finished 1-1.
The total shots of 27 in the game was also the most since that match (29)
Needless to say Barnsley once again enjoyed more ball possession than their opponents (56%-44%) - still no side has enjoyed more ball possession than Barnsley this season, however this was their lowest amount in five matches (all comps)
Barnsley have now only lost once in their last 14 home league meetings with Portsmouth (W10 D3), a 4-1 defeat in September 2001.
This was only the second meeting home or away in 15 that has ended level and the first since an incredible 4-4 draw at Fratton Park in February 2002.
This was the first Oakwell meeting drawn since November 1995 which ended 0-0.
1. Adam Davies (c)
12. Dimitri Cavaré
5. Ethan Pinnock
18. Adam Jackson
23. Dani Pinillos
20. Brad Potts
27. Alex Mowatt
8. Cameron McGeehan
10. George Moncur
25. Cauley Woodrow
19. Kieffer Moore
33. Jacob Brown (for Cavaré 45)
11. Lloyd Isgrove (for Moncur 63)
26. Mamadou Thiam (for Potts 80)
6. Liam Lindsay, 21. Mike-Steven Bähre, 29. Victor Adeboyejo, 35. Jake Greatorex
15. Craig MacGillivray
20. Nathan Thompson
16. Jack Whatmough
5. Matthew Clarke
3. Lee Brown
7. Tom Naylor
32. Ben Thompson
10. Jamal Lowe
26. Gareth Evans (c)
11. Ronan Curtis
9. Oliver Hawkins
2. Anton Walkes (for Curtis 75)
6. Christian Burgess, 8. Brett Pitman, 17. Dion Donohue, 33. Ben Close, 37. Andre Green, 35. Alex Bass.
Sky Bet League One results:
Saturday 15th December 2018:
BARNSLEY 1-1 Portsmouth
Doncaster Rovers 3-0 Scunthorpe United
Bradford City 4-0 Walsall
Charlton Athletic 2-0 AFC Wimbledon
Coventry City 1-2 Luton Town
Clarke-Harris pen 90+5
Fleetwood Town 1-0 Burton Albion
Evans pen 51
Gillingham 2-2 Wycombe Wanderers
Oxford United 2-0 Blackpool
Rochdale 1-2 Plymouth Argyle
Perkins og 80
Shrewsbury Town 2-2 Peterborough United
Southend United 3-0 Accrington Stanley
Sunderland 2-1 Bristol Rovers
Barnsley lie 7th in Sky Bet League One with 36 points from 21 games. We are 2 points off the Play-Offs, 8 points off the Automatic Promotion Places, 12 points off First Place and 16 points above the Relegation Zone.
Up to 16/12/18
On The Road:
Sky Bet League One Matchday Twenty Two: Blackpool v Barnsley, Saturday 22nd December 2018. Kick-Off: 3pm
Sky Bet League One Matchday Twenty Three: Barnsley v Peterborough United, Wednesday 26th December 2018. Kick-Off: 3pm