The P-11 was designed by Swedish-bornGeorge Kellgren, the designer of many earlier Husqvarna (Sweden), Intratec, and Grendel brand firearms. The P-11 uses an aluminum receiver inside a polymer grip housing held on with polymer pins. The slide, barrel, and magazine are steel. The standard magazine holds ten rounds, or twelve rounds in states not limited to 10 round magazines. Both fit flush to the bottom of the pistol. At 14 oz (400 g) unloaded, the handgun itself is comparatively light. The P-11 lacks an external manual safety relying instead on a long and heavy double action only (DAO) trigger pull, which requires nine pounds of pressure, to prevent accidental discharge. A firing pin spring and low-mass hammer prevent discharge if the gun is dropped. The P-11 will also accept some Smith and Wesson 59 series magazines. An available adapter wraps around the base of 15-round Smith & Wesson model 59 style magazines. Smith & Wesson series 69 compact 12 round magazines will also work, with a matching short adapter sleeve as well. Accessories such as trigger shoes, finger-rests, belt clips, steel guide rods to replace the factory installed polymer guide rod, gray and OD green colored polymer grip housings, night sights and other accessories are also available from the manufacturer.
For a short period, the P-11 was offered in .40 S&W and .357 Sig with reduced magazine capacity. These weapons were designated P-40 and P-357. These models mated a P-11's frame to a larger slide width and barrel. Kel-Tec has suspended production of these pistols and conversion kits. In 2006, Kel-Tec introduced a single-stack pistol based on the P-11 with engineering improvements borrowed from the P-3AT. The resulting PF-9 pistol weighs about the same loaded as the P-11 empty and is somewhat slimmer.
The P-11 is designed for concealed carry by members of the general public and law enforcement officers. It is only slightly wider than the staggered-column magazine it uses. It is particularly attractive to users who want a concealable firearm but also desire a "full-power" defensive cartridge. The barrel is near the minimum length possible with a Browning tilting-barrel system of operation. The gun easily fits into a pocket, small holster, or inside a handbag. All edges are rounded and smoothed allowing comfort while carrying concealed. There are few protrusions on the pistol to catch on a pocket holster, a deep concealment or inside of waistband holster.