The UMP is a blowback-operated, magazine-fed submachine gun firing from a closed bolt.[6]

As originally designed, the UMP is chambered for larger cartridges (.45 ACP and .40 S&W) than other submachine guns like the MP5, to provide more stopping power against unarmoured targets (with slightly lower effectiveness at longer range) than the MP5 (largely offered in 9×19mm, albeit with short-lived production of 10mm Auto and .40 S&W variants). A larger cartridge produces more recoil, and makes it more difficult to control in fully automatic firing. To mitigate this, the UMP has a cyclic rate of fire of around 600–700 rounds per minute (RPM), it is worth to mention that the rate of fire increases if (+ P) ammunition is used.[7] This makes it one of the slowest firing modern submachine guns in the market.[6]

The UMP9 (the 9×19mm version of the UMP) is almost 0.2 kilograms (0.44 lb) lighter than its MP5 counterpart. Its predominantly polymer construction reduces both its weight and the number of parts susceptible to corrosion.[6][8]

The UMP is available in four trigger group configurations, featuring different combinations of semi-automatic, 2-round burst, fully automatic, and safe settings. It features a side-folding buttstock to reduce its length during transport. When the last round of the UMP is fired, the bolt locks open, and can be released via a catch on the left side. The standard viewing sights are composed of an aperture rear sight and a front ring with a vertical post. It can mount four Picatinny rails (one on top of the receiver, and one on the right, left, and the bottom of the handguard) for the attachment of accessories such as optical sights, flashlights, or laser sights. Vertical fore-grips can be attached to the bottom rail for increased control during burst and automatic fire.[6]