Although the club is based in Schleswig-Holstein, the teams of Union participate in the league system of the Hamburg Football Association.

The men's team played in the second-highest Hamburg amateur league from 1948 to 1952, from 1953 to 1955, and from 1964 to 1969, mostly oscillating between the Bezirksliga and Kreisliga.

In the mid-2010s, the club experienced a sporting upswing, with renewed promotion to the Bezirksliga in 2014 and to the Landesliga two years later.

As Oberliga champion Altona 93 gained promotion to the Regionalliga Nord and Wedeler TSV withdrew their team from the Oberliga, a decisive match was played between the third-placed teams from the two Landesliga divisions.

The greatest successes were the runner-up finishes in 2016 and 2017 behind FC St. Pauli and Walddörfer SV, respectively.