Starting at the front with a new manager Urs Fischer, who has won numerous titles in the Swiss Super League with FC Basel; this was only the beginning of a new Union squad that saw drastic changes from the season before.

Union would start the new campaign without fan favorite Steven Skrzybski but added key players such as Rafal Gikiewicz and Sebastian Andersson, both of whom would go on to feature in every fixture.

Bundesliga season with a 1–0 win at home to start the campaign, courtesy of a late free kick goal by former captain Felix Kroos.

This impressive early-season run had Die Eisernen remaining undefeated in their first 17 games in 3rd place, within striking distance of promotion heading into the winter break to the surprise of many.

In the first matchday of the 2nd half of the season, Union fans were met with a worrying result, losing the first game back in a 0–3 collapse to midtable Erzgebirge Aue.

On matchday 31 a 2–0 win against Hamburger SV in the near-impenetrable fortress that was the Stadion An der Alten Försterei launched Die Eisernen back into the top three, good enough for a playoff against the 16th place Bundesliga team for a chance at promotion.

However, their amazing home form and ability to draw on the road was enough, as they secured a place in the Bundesliga Relegation playoffs, facing off in a two-leg series against VfB Stuttgart.

Stuttgart took a 1–0 lead just before halftime thanks to Christian Gentner, but 89 seconds later Suleiman Abdullahi managed to reply with an assist from Sebastian Andersson, and all was level at the break.

They came back strong, played out their chances and in the 68th minute Marvin Friedrich tied the game up at 2–2 from a corner kick by Christopher Trimmel.

Union fans we’re pleased with the 2–2 draw, since the away goals rule was in effect for these playoffs and Stuttgart had to come to Berlin and manage to find a win that had eluded virtually all visitors during the campaign.

Somewhat controversially, it was promptly taken back by the video assistant referee, as Nicolás González had been found to have obstructed Gikiewicz's view from an offside position, thus making the goal unofficial.

The success in the promotion playoff cemented the 2018–19 season as the most famous ever in club history to this date, and simply a night no Union Berlin fan was ever going to forget.

The following week Union paraded around the streets of Berlin and even down the Spree on a team boat, culminating in a party for players and fans alike at the Stadion An der Alten Försterei.