They will have to do it all again after this firey FA Cup first round stalemate at Priestfield Stadium.
Mattie Pollock's first goal for the club handed Michael Duff's side a deserved lead at the break but they were pegged back in the second half by substitute Gerald Sitole.
That means a fifth match against Gillingham this term after the Carabao Cup tie here back in August, which also ended in a goal apiece, although on that occasion the Robins came out on top in the resulting penalty shoot-out.
"I'm disappointed because I thought we had done enough to win the game," Duff said afterwards.
"We've got to learn from it, going one-nil up. They equalised from passing the ball so we need to grow from this.
"It's a difficult place to come. It probably shows how far we've come that we're disappointed with a draw away at Gillingham. It was a scrappy game and the wind didn't help.
"Overall, a tinge of frustration."
There was one change, Christian Norton came in and Liam Sercombe dropped to the bench. Duff named eight of his permitted nine subsitutions of which he could use five. Will Armitage, the 16-year-old defender who scored in the Under-18s' FA Youth Cup 3-0 win on Wednesdsay evening, was one.
His side started brightly enough, enjoying a lot of the ball in the opening exchanges, creating a handful of chances and deserving their lead at the break.
A couple of early Chris Hussey corners caused some panic in the Gillingham defence while Ryan Jackson and Danny Lloyd went close at the other end, the latter denied by a diving Scott Flinders stop. There was also a good shout for a penalty kick after some clever play by Norton but the referee was unimpressed.
But the breakthrough arrived 11 minutes before the interval after Kyle Vassell's 20 yarder had drawn the first meaningful save by Aaron Chapman, the Gillingham number one. He turned the effort around for another corner, which provided another opportunity for Hussey to deliver a menacing ball to the far post where Pollock arrived to head home.
A well worked moved on the stroke of half-time almost handed the hosts an unlikely equaliser, but Vadaine Oliver couldn't keep his effort on target. Alfie May pulled a long ranger a foot wide moments later.
Ben Reeves forced Flinders into a smart stop with a 25-yard free-kick five minutes into the second half, which was a more firey affair with Ellis Chapman and Duff shown yellow cards after a late challenge by the midfielder.
The equaliser arrived after 59 minutes when Jackson's fancy footwork created the space to cross from the right, finding substitute Gerald Sithole who produced a neat finish to beat Flinders to his left.
The Gills held the initiative so Duff rang the changes, sending on Sercombe (for May), Dan Crowley (Vassell) and Kyle Joseph (Norton) and it had the desired effect with his side enjoying the lion's share of possession for the remainder of the contest.
But despite their strong finish, it was Bailey Akehurst with the best chance of the closing stages, a strike that fizzed past the left post with Finders beaten. The Robins were also indebted to a fine last ditch tackle by Lewis Freestone to thwart a dangerous counter attack in the final seconds.
GILLINGHAM (4-4-2): Chapman; Jackson (Lintott 79), Ehmer, Bennett (Akinde 72), McKenzie (Akehurst 56); Dempsey (c), Adshead (Sithole 46), Tucker; Reeves; Oliver. Subs not used: Cumming (Gk).
CHELTENHAM TOWN (3-5-2): Flinders; Long (c), Pollock, Freestone; Blair, Thomas, May (Sercombe 67), Chapman, Hussey; Vassell (Crowley 77), Norton (Joseph 77). Subs not used: Evans (Gk), Williams, Horton, Barkers, Armitage.
REFEREE: A Woolmer