Barnsley picked up their first away win of the season, at the fifth time of asking - the longest it has taken them to break their away duck since 2013-2014 when they did not win away until the ninth away game.
It is the second time in three years that Millwall has become Barnsley's first away win as they won 3-2 at the Den in 2015-2016 in their second away match.
From when the two sides met at Wembley in the play-off showpiece 14 months ago only three players started for Millwall yesterday (goalkeeper Jordan Archer and strikers Steve Morison and Lee Gregory) whilst only two of the Barnsley 11 that day started yesterday (Adam Davies and Adam Hammill)
The Reds have a remarkable record over the Lions and have now beaten them five successive times, including each of the last two at the Den. They have actually won four of the last five meetings in London if you include the 2016 League One Play-Off Final.
Barnsley's last two results against Millwall have both been 3-1 wins, it is the first time they have achieved the same result back to back against one team since they beat Blackburn 2-0 home and away last season.
This victory along with the one at Ewood Park in April are the only two away wins Barnsley have managed in their last 12 outings. They have won three of the last 13 and all three have been by a two goal margin (3-1 at Villa, 2-0 at Blackburn) 3-1 at Millwall)
Prior to this game, Barnsley had the joint worst away record in the division along with Birmingham, however this victory sees them leapfrog Burton, Bolton, Hull, QPR and Millwall in those stakes.
The first two goals were scored by Tom Bradshaw following assists from Harvey Barnes, it is the first time one Reds player has set up another twice in one game since Conor Hourihane provided two assists for Sam Winnall in a 3-0 win at Birmingham in December.
It is Bradshaw's second brace for the club, with his other also coming in a 3-1 away win- at Aston Villa in February.
Barnsley opened the scoring in two successive league games for the second time this season - also v Ipswich and then Nottingham Forest in August. It is the first time this season they have opened the scoring on the road.
Two of the game's goals were penalties (Lee Gregory netting for Millwall and Mamadou Thiam opening his Reds account) It is the first time that both Barnsley and their opponent have scored a penalty in the same match since April 2011 when Andy Gray scored one for Barnsley and Nicky Maynard netted one for Bristol City in a 4-2 win for the Reds.
Prior to the game Barnsley were the only side in the Championship to have had 100% of their goals scored by British players this season (Wales 4, England 6) but Senegal striker Thiam's penalty ends that run.
Thiam's penalty was also only the second goal scored by a Barnsley substitute in the Championship this season - Ryan Hedges with the other in the opening day defeat at Bristol City.
Five goals have been scored in the final ten minutes in Barnsley's last three matches (two for three against)
Barnsley had nine shots on target at the Den, their most away from home since having ten at Molineux in 4-0 win over Wolves in September of last year.
Barnsley won two corners, the exact same amount as they have won in three of their previous four away league games, the only exception this season being at Wolves where they won eight.
George Moncur failed to appear for the first time this season whilst summer signing Cameron McGeehan made his first competitive start since January (for Luton). He picked up a booking yesterday which means he has been shown a yellow card in each of the last three matches he has started.
Ryan Hedges (for Barnes 72)
Mamadou Thiam (for Bradshaw 72)
Jared Bird (for McGeehan 81)
Nick Townsend, Zeki Fryers, Angus MacDonald, Ike Ugbo.
Sky Bet Championship results:
Friday 29th September 2017:
QPR 1-2 Fulham
Robinson 41 og, Johansen 85
Saturday 30th eptember 2017:
Aston Villa 1-0 Bolton
Kodjia pen 39
Burton 0-4 Wolves
Jota 5, Saiss 11, Vinagre 41, Bonatini 62
Cardiff 0-0 Derby
Hull 6-1 Birmingham
Campbell 7 Gallagher 90+1
Meyler pen 11
Ipswich 1-3 Bristol City
Waghorn 41 Brownhill 2, Diedhiou 31, Reid 82
Middlesbrough 2-2 Brentford
Braithwaite 68 Barbet 29, Watkins 72
Millwall 1-3 BARNSLEY
Gregory pen 42 Bradshaw 40, 60 Thiam pen 83
Nottingham Forest 2-1 Sheffield United
Cummings 9 Lundstram 3
Preston 2-2 Sunderland
Harrop 55 Honeyman 28, McGeady 59
Reading 1-2 Norwich
Moore 13 Maddison 10, Jerome 52
Sunday 1st October 2017:
Sheffield Wednesday 3-0 Leeds
Barnsley lie in 18th place in the Sky Bet Championship with 11 points from 10 games.
We are 9 points outside the Play-Offs, 12 points off the Automatic Promotion Places, 13 points off First place and 3 points above the Relegation Zone.
Up to 01/10/17
Sky Bet Championship Matchday Eleven: Barnsley v Middlesbrough, Saturday 14th October 2017. Kick-Off: 3pm
On The Road:
Sky Bet Championship Matchday Thirteen: Sheffield Wednesday v Barnsley: Saturday 28th October 2017. Kick-Off: 12:30pm
Millwall 1-3 Barnsley