The Bees will enter the contest off the back of a 2-2 draw with Nottingham Forest in the Premier League on Saturday, while Gillingham drew 1-1 with Fylde in the first round of the FA Cup.
Match preview
Brentford were on the verge of securing all three points against Forest in the Premier League on Saturday afternoon, with Yoane Wissa's 75th-minute effort sending Thomas Frank's side into a 2-1 lead.
However, an own goal from Mathias Jorgensen in the 96th minute earned a point for Forest, with the result leaving the Bees in 10th spot in the table on 16 points.
Frank's side will now switch their attention to the EFL Cup, and they secured their spot in this round of the competition courtesy of a 2-0 victory over Colchester United at the end of August.
Cup success will not be seen as a priority for the club this season, rather securing another campaign of Premier League football, but it will give a number of squad players the chance to earn some valuable minutes.
Brentford last faced Gillingham in January 2014, recording a 2-1 victory in the League One contest, while the Bees have not lost to their opponents on Tuesday night since a League One contest back in March 2007.
Gillingham, meanwhile, were held to a 1-1 draw by non-league Fylde in the first round of the FA Cup on Saturday afternoon, meaning that the two sides will lock horns in a replay on November 15.
Neil Harris's side are winless in their last five matches in all competitions, which includes defeats in their last two League Two matches against Leyton Orient and Doncaster Rovers.
Gillingham have found it difficult in the league this season, only picking up 13 points from their 16 matches, which has left them down in 20th spot in the table, just one point above the relegation zone.
The Gills are next in League Two action on Saturday against high-flying Northampton Town, and it is an important few weeks for the club, as they could potentially progress or be knocked out of two cup competitions.
Gillingham actually had less possession (47%) and less attempts (eight to 11) than Fylde in the FA Cup on Saturday, so the club's supporters will be demanding an improvement against Brentford on Tuesday night.
Brentford EFL Cup form:
W
Brentford form (all competitions):
L
W
D
L
D
D
Gillingham EFL Cup form:
W
W
Gillingham form (all competitions):
W
D
D
L
L
D
Team News
Brentford will again be without the services of Aaron Hickey, Thomas Strakosha and Pontus Jansson for Tuesday's contest with Gillingham on home soil, but Ivan Toney is available again following suspension.
Head coach Frank will make changes to the side that started against Forest in the league, with Jorgensen, Frank Onyeka, Mikkel Damsgaard and Sergi Canos among those expected to start.
Wissa could lead the line for the Premier League side, with Bryan Mbuemo likely to drop to the bench alongside Ethan Pinnock, Mathias Jensen and Josh Dasilva.
As for Gillingham, head coach Harris will need to assess the fitness of his players following the FA Cup contest on Saturday, but there are not expected to be wholesale changes for this match.
A 4-4-2 formation should again include Mikael Mandron and Lewis Walker in the final third of the field.
However, there could be a change in midfield, with Max Ehmer potentially coming in for Dominic Jefferies, while Cheye Alexander might also come into the XI on Tuesday night.
Brentford possible starting lineup:
Raya; Rasmussen, Jorgensen, Mee, Henry; Onyeka, Janelt; Lewis-Potter, Canos, Damsgaard; Wissa
Gillingham possible starting lineup:
Morris; McKenzie, Wright, Baggott, Law; Alexander, Ehmer, O'Keefe, MacDonald; Mandron, Walker
We say: Brentford 2-0 Gillingham
Gillingham are not in the best of form, and they are unlikely to get much change out of Brentford on Tuesday night. The Bees are not expected to be at full strength but should have too much quality for their League Two opponents in this contest.