The Heckler & Koch MK 23, Mk 23 Mod 0, Mark 23, or MARK 23, is a handgun consisting of a match grade semi-automatic pistol, a laser aiming module (LAM), and suppressor. The MK 23 is considered a match grade pistol, and is capable of making a 2-inch (51 mm) group at 50 yards (46 m), roughly 4 MOA. The MK 23 has exceptional durability in harsh environments, being waterproof and corrosion-resistant. It uses a polygonal barrel design, which is reported to improve accuracy and durability. It also features an ambidextrous safety and magazine release on both sides of the frame. The magazine release is at the rear edge of the trigger guard, which is wide enough to allow the use of gloves. A decocking lever is on the left side, which will silently lower the cocked hammer. The MK 23 is part of a larger weapon system that includes an attachable laser aiming module, a suppressor, and some other features such as a special high-pressure match cartridge (.45 +P ammunition).

Season 3

A Heckler & Koch Mark 23 is used with a suppressor by Mike Ehrmantraut in Full Measure to infiltrate a Juárez Cartel facility to interrogate Duane Chow.

Season 4

Mike uses the Mark 23 again in Bullet Points Ciudad Juárez cartel gunmen who ambush a refrigerated truck transporting methamphetamine (though he uses it without the suppressor in this episode).