Having overcome Championship outfit Stoke City 4-0 in the third round, Brendan Rodgers' Foxes face more second-tier opposition having been matched up against promotion-chasing Brentford away from home.
Meanwhile, the draw for the fifth round of the competition also took place, with Leicester set to take on either Premier League rivals Brighton & Hove Albion or League One side Blackpool at the King Power Stadium should they overcome the Bees.
All fourth-round ties are to take place over the weekend of the 23rd of January, whilst fifth round fixtures are scheduled for Wednesday 10th February.
Same opponents, new ground
The Foxes' meeting with Brentford represents an exact repeat of the same fixture last season. Travelling to Griffin Park, Leicester ran out slender winners thanks to an early Kelechi Iheanacho strike.
The main difference this time around though is that the clash will be played at the Bees' new ground, the Brentford Community Stadium.
Leicester have not actually tasted defeat against the Bees since 1953, having won six out of their last seven meetings. The Foxes have also never lost an FA Cup fixture to their latest opponents so will head to the capital in a confident mood.
Should Brendan Rodgers guide his side through to the fifth round, then a somewhat favourable draw awaits. Having avoided all of the so-called Premier League big-six, either Blackpool or Brighton are set to travel to the King Power Stadium.
Leicester have already squared off with the Seagulls in the top flight this season and secured one of their most comfortable wins of the campaign in a 3-0 victory.
If their opponents transpire to be Blackpool, it will be the first time that the teams have come together since a 3-1 success for the Foxes in the Championship during the 2013/14 season.