A device for arranging an accessory on a firearm, in particular a handgun, is provided, wherein the device has a housing for receiving the accessory in the housing, wherein the housing can be fastened to the firearm, wherein the housing has a first portion with a front end wall and with a rear end wall at a distance from the front end wall, the housing has a second portion, which protrudes axially at the rear end wall of the first portion, the second portion has a fastening device for fastening the housing to the firearm, and the housing has a substantially L-shaped basic form. A firearm with a device for arranging an accessory on a firearm that is arranged on it or can be arranged on it is also provided.