The hosts are in fifth place with 14 points from seven games and beat Holstein Kiel 2-0 on October 20, while Frankfurt lost 2-1 against Leverkusen and the result left them in sixth place with 13 points.
Match preview
The home side have arguably been the Bundesliga's surprise package this term, as while they had finished fourth in 2022-23, they ended last season fourth last in 15th place with just 33 points.
Union Berlin are on track to accumulate 68 points this campaign while conceding fewer than 20 goals, and that would be a significant improvement considering they conceded 58 times in the league last season.
In their match against Holstein Kiel, the Iron Ones were especially dominant in the first half, restricting their opponents to just one shot from open play.
Manager Bo Svensson will be delighted with his side's form so far this campaign given his team have won three of their last four matches in the league, including against Nuri Sahin's Borussia Dortmund.
Svensson's team have also won their last four Bundesliga home games, scoring seven times and conceding on three occasions in that period.
As for the visitors, they will be disappointed by their defeat against Leverkusen considering the Eagles had taken a 1-0 lead thanks to Omar Marmoush's penalty in the 16th minute, but eventually lost due to Victor Boniface's 72nd-minute winner.
Eintracht Frankfurt have not won in their last two league games, though the match prior to their defeat against the champions was a 3-3 draw with Bayern Munich on October 6.
Die Adler beat RFS 1-0 in the Europa League on Thursday, but they only scored the winner in the 79th minute despite producing 20 shots
Boss Dino Toppmoller's side are four points from first-placed Bayern, and their record of 15 goals netted and 11 goals conceded makes them the division's third best offensive and joint fifth best defensive team.
Frankfurt have won just once in their last three games, but they did win five of the previous six fixtures in all competitions.
Toppmoller's side have performed well away from home this term, winning four and losing two of their six matches on the road, although they have lost five of their last eight away fixtures in the Bundesliga.
Union Berlin Bundesliga form:
W
D
W
L
W
W
Eintracht Frankfurt Bundesliga form:
W
W
W
W
D
L
Eintracht Frankfurt form (all competitions):
D
W
W
D
L
W
Team News
Union Berlin are likely to be without numerous players on Sunday, including goalkeeper Frederik Ronnow and midfielder Laszlo Benes until late November.
The hosts will also be unable to select Ivan Prtajin and Yannic Stein until next month, while Josip Juranovic, Lucas Tousart and Jordan Pefok are considered doubts.
Svensson could start a back three consisting of Danilho Doekhi, Kevin Vogt and Diogo Leite, and he may field Aljoscha Kemlein and Rani Khedira in midfield.
Meanwhile, Eintracht Frankfurt have considerably fewer availability concerns, with midfielder Oscar Hojlund ruled out due to a broken ankle.
As for who Toppmoller might start, expect Tuta and Robin Koch to start as centre-backs behind a double pivot of Junior Dina Ebimbe and Hugo Larsson.
Omar Marmoush is certain to start in attack, and he may be joined in the forward line by Hugo Ekitike.
Union Berlin possible starting lineup:
Schwolow; Doekhi, Vogt, Leite; Trimmel, Kemlein, Khedira, Rothe; Hollerbach, Jeong, Vertessen
Eintracht Frankfurt possible starting lineup:
Trapp; Kristensen, Tuta, Koch, Theate; Gotze, Ebimbe, Larsson, Nkounkou; Marmoush, Ekitike
We say: Union Berlin 1-1 Eintracht Frankfurt
Given Union Berlin's excellent defensive record, it is difficult to see them conceding more than once on Sunday.