The ships of the class were armed with ten 10.5 cm SK L/40 guns in single mounts.
Two were placed side by side forward on the forecastle, six were located amidships, three on either side, and two were placed side by side aft.
The guns could engage targets out to 12,200 m (40,026 ft 3 in).
For defense against torpedo boats, they were armed with ten 3.7 cm (1.5 in) Maxim guns.
They were supplied with 1,500 rounds of ammunition, for 150 shells per gun.
Later in their careers, Bremen and Lübeck had two 15 cm SK L/45 guns installed in place of the two forward and two rear 10.5 cm guns.
They retained the six broadside 10.5 cm guns.
All seven ships were also equipped with two 45 cm (17.7 in) torpedo tubes with five torpedoes.
These tubes were submerged in the hull on the broadside.
Lübeck later had a pair of 50 cm (20 in) torpedo tubes installed in deck mounts, with four torpedoes.

Armor protection for the members of the class consisted of two layers of steel with one layer of Krupp armor.
The ships were protected by an armored deck that was up to 80 millimeters (3.1 in) thick.
Sloped armor 50 mm (2.0 in) thick gave some measure of vertical protection, coupled with the coal bunkers.
The conning tower had 100 mm (3.9 in) thick sides and a 20 mm (0.79 in) thick roof.
The ships' guns were protected by 50 mm thick shields.
The ships of the class were armed with ten 10.5 cm SK L/40 guns in single mounts. Two were placed side by side forward on the forecastle, six were located amidships, three on either side, and two were placed side by side aft. The guns could engage targets out to 12,200 m (40,026 ft 3 in). For defense against torpedo boats, they were armed with ten 3.7 cm (1.5 in) Maxim guns. They were supplied with 1,500 rounds of ammunition, for 150 shells per gun. Later in their careers, Bremen and Lübeck had two 15 cm SK L/45 guns installed in place of the two forward and two rear 10.5 cm guns. They retained the six broadside 10.5 cm guns. All seven ships were also equipped with two 45 cm (17.7 in) torpedo tubes with five torpedoes. These tubes were submerged in the hull on the broadside. Lübeck later had a pair of 50 cm (20 in) torpedo tubes installed in deck mounts, with four torpedoes.
Armor protection for the members of the class consisted of two layers of steel with one layer of Krupp armor. The ships were protected by an armored deck that was up to 80 millimeters (3.1 in) thick. Sloped armor 50 mm (2.0 in) thick gave some measure of vertical protection, coupled with the coal bunkers. The conning tower had 100 mm (3.9 in) thick sides and a 20 mm (0.79 in) thick roof. The ships' guns were protected by 50 mm thick shields.
Bremen-class cruiser