BARNSLEY are two points behind joint leaders Peterborough and Portsmouth after dominating this Oakwell encounter.
They enjoyed two-thirds of the possession and rattled in 25 shots, seven of which were on target.
More importantly, Kieffer Moore struck twice to make it six goals for the season and ensure Barnsley maintained their unbeaten start against a stubborn Gillingham.
Barnsley head coach Daniel Stendel claimed: “We had control of the game, we had control of the opponent. We had a lot of chances to score and at 2-0 in front I was very satisfied then we had one moment where we went to sleep.
“I was a little bit surprised but it is what it is. The last 20 minutes weren’t easy for us but it was a good win.”
The Reds started on the front foot and took the lead after 13 minutes when Moore unleashed a thunderous effort from 20 yards, beating goalkeeper Tomas Holy at his near post.
I was a little bit surprised but it is what it is. The last 20 minutes weren’t easy for us but it was a good win.Daniel Stendel
Barnsley doubled their advantage in the 33rd minute when Elliott List was adjudged to have fouled George Moncur inside the area and Moore stepped up to slot the penalty down the middle.
Gillingham thought they had got one back on the stroke of half-time. From a set-piece, the ball fell to Brandon Hanley, who slid the ball across for Tom Eaves to net only to be flagged offside.
The Gills finally got one back on the hour. Adam Davies saved at point-blank range, but after a scramble, Josh Parker forced the loose ball over the line.
Barnsley: Davies, Cavare, Pinnock, Lindsay, Pinillos, Dougall, Potts (Adeboyejo 62), Mowatt, Moncur (McGeehan 73), Thiam (Brown 81), Moore. Unused substitutes: Jordan Williams, Isgrove, Walton, Jackson.
Gillingham: Holy, Fuller, Zakuani (Lacey 40), Ehmer, Garmston, Hanlan (Wilkinson 67), Reilly, Bingham, Parker, Eaves, List (Rees 56). Unused substitutes: O’Neill, Nasseri, Stevenson, Hadler.
Referee: J Busby (Oxfordshire).