A magazine adapter for use in a firearm includes a magazine adapter body configured to be bottom-fed and detachably received within a magazine well on the firearm. The magazine adapter body has a bottom panel, an upwardly extending first panel and an upwardly extending second panel defining a channel therebetween proportioned to slidably receive a magazine therein. The second panel defines a groove configured to engage a firearm magazine catch on the firearm when the magazine adapter body is received within the magazine well. The magazine adapter body may detach from the magazine well when the firearm magazine catch is actuated. The first panel includes an adapter magazine catch configured to releasably engage the magazine when the magazine is received within the magazine adapter channel. A magazine release is coupled to the adapter magazine catch. The adapter magazine catch disengages from the magazine when the magazine release is actuated.