Town let wasted chances get the better of them as they lose their first home game of the season.
It was an early opener from Connor Mahoney in the 22nd minute with a deflected effort being the difference between the two sides.
Swindon named a single change to the starting 11 that drew to Salford with a suspended Tom Brewitt being dropped for Harrison Minturn, the only change to the bench being Jake Cain being dropped for Liam Kinsella
It was Swindon who had the best of the earlier chances as within the first ten minutes they would witness two shots from inside the area by Jake Young and Dan Kemp blocked amazingly by their defence.
However, it wouldn’t be Swindon who hit first as a goal from Connor Mahoney would come soon after, as the tricky winger managed to cut in on his left foot and let off a shot that would be deflected and mis-foot Murphey Mahoney, who could only watch it roll into the back of the net.
It would be the start of the Jake Turner show in the 26th minute as Kemp would play a pinpoint ball to Young who’s first time effort was saved incredibly by the young goalkeeper.
Charlie Austin would be close to scoring on his 100th appearance as another cross from Kemp would fall to the Swindon captain whose glancing header would go whiskers past the right-hand post.
However, it would be Mahoney who would be the hero next as a mixup as the back for Town saw Macauley Bonne through on goal but a fantastic, outreached arm would keep Swindon in the game.
Half-time: Swindon Town 0-1 Gillingham
The first half ending would be replicated in the start of the second as powerful shot from the edge of the box from Gillingham would be saved with fingertips by Mahoney.
Remeao Hutton would be the next person to add to the list of nearly goals scored as himself and Kemp would play a brilliant 1-2 on the edge of the box that would end in with Hutton managing to curl a brilliant shot towards the bottom left but again Turner would keep Gillingham ahead.
After plenty of chances for Swindon it would be Gillingham with the next major chance as they would receive a penalty as Fraser Blake-Tracey would make a last-ditch tackle unsuccessfully.
It would be Cheye Alexander who stepped up for the penalty kick and would put it wide of the left-hand post, giving Swindon a lifeline.
With the game getting closer to an end, Swindon would have to dig deep to try and get a result, and that they did do with Kemp showing his dribbling ability by beating a couple of defenders until eventually unleashing a venomous shot that yet again would be saved by Turner.
The last chance of the game would fall to none other than Jake Young as a floating cross would find the man in form, but unfortunately for him would also manage to get under the ball and put it over the bar, only for the final whistle to come a couple minutes later.
Swindon Town will now be looking forward to their League 2 clash this coming weekend against MK Dons, as Town look to regain some form.
Gillingham: Turner, Alexander, Mastersons, Williams (Lapslie 62), Jeffries, Malone (C), Clarke (Ehmer 76), Coleman, Mahoney (S.Wiliams 81), Ogie, Bonne (Nichols 81)
Goals: Mahoney (22)
Subs not used: Morris, Clark, Orsi
Swindon Town: Mahoney, Hutton, Blake-Tracy, McEachran, Young, Khan, Kemp, Minturn (Clayton 80), Godwin-Malife, Shade (Obodo 88), Austin (C) (Hepburn-Murphy 69)
Subs not used: L.Ward, Genesini, Kinsella
Referee: Peter Wright
Attendance: 8,853 (610 Away Fans)